Shaykh al-'Allāmah Sulaymān al-'Alwān advised that tullāb al-'ilm memorise one or two matn in each of the Islamic sciences and he mentioned examples of what one may memorise:

Tawhid: al-Usūl ath-Thalāthah, Kitab at-Tawhīd, al-'Aqīdah al-Wāsitiyyah.

Hadith: al-Arba'īn an-Nawawiyyah, then 'Umdat-al-Ahkām, and then Bulūgh-al-Marām.

Usūl al-fiqh: al-Waraqāt, then Marāqi as-Sa'ūd or it's abdrigment.

Qawā'id al-Fiqh: The Mandhūmah of as-Sa'di.

Mustalah al hadīth: al-Bayqūniyyah.

Nahw: al-Ajurumiyyah, then Qatr-an-Nadā or Mulhat-al-I'rāb, then The Alfiyyah of ibn Mālik....or if one goes from al-Ajurumiyyah to Alfiyyah directly there is no harm in that, but going step by step is desirable.

Fiqh: ad-Durar al-Bahiyyah by ash-Shawkāni.

Usūl-at-Tafsir: Muqaddimah of ibn Taymiyyah.

Source:
https://youtu.be/Xh-K2D-hKKY

The Eighth Nullifier of Islam - Supporting and Aiding the mushrikīn Against the Muslims - Shaykh Khālid al-Fulayj (حفظه الله)

https://youtu.be/3K-mdyBp2hA?feature=shared

Notes on Fiqh matters (Tahārah, Salāh, Janāzah, Fasting, Hajj) - taken from the words of Shaykh Sulaymān al-'Alwān (فك الله أسره)

Detailing of when ignorance is an excuse & prevents takfīr - Shaykh Khālid al-Fulayj (حفظه الله)

https://youtu.be/BrxkPuEIXwE?feature=shared

The Abandoned Obligation - the words that got Shaykh 'Abdullah as-Sa'd imprisoned.

(Recording is from during US occupation of Iraq)

https://youtu.be/5xvKsF8yanM?feature=shared

Ruling on those who give excuse of ignorance in major shirk - Shaykh 'Ali al-Khudayr (فك الله أسره)

https://youtu.be/tn_Cs4KsRjA?feature=shared

Takfīr of Excuser after Hujjah - Sheikh Khālid al-Fulayj (فرج الله عنه) on Fatwa of ibn Baz.
https://youtu.be/rP4JVabm_bw?feature=shared

Houthi/Shi'ah tawāghīt's fake concern for Palestine - Adel el Shony
https://youtu.be/6HcEj9E35io?feature=shared

Sheikh Hamūd ibn 'Uqlā ash-Shu'aybi (رحمه الله) :

The problem now is that people say the Ashā'irah are the closest people to ahl as-Sunnah; while knowing that if you look at them in terms of the attribute of speech, you find that they're in agreement with the Mu'tazilah [claiming] that Allah didn't speak nor say [anything]. And if you look at them in terms of al-qadar and the actions of the slaves, you find that they are Jabriyyah as they negate that the slave has actions. And if you look at them in terms of the attributes, you find that they are Jahmiyyah except for what they claim to affirm of seven attributes. So where is the closeness to them? for they are far away from ahl as-Sunnah, very far.


[Sharh al-'Aqīdah at-Tahāwiyyah p.48]

The Ruling on those who support the Rāfidha against ahl as-Sunnah - Sheikh Khālid al-Fulayj (فك الله أسره)

https://youtu.be/dpeGq1i8Kfo?feature=shared

Sheikh al-Muhaddith 'Abdullah as-Sa'd (حفظه الله):

Sheikh-ul-Islām [ibn Taymiyyah] reported an ijmā' of the sahābah that the khawārij are not ruled as kuffār; and it is the correct view. When the tābi'īn came they differed in regard to takfīr of the khawārij, and likewise [the tabi'īn differed] in regard to takfīr of al-Hajjāj [ibn Yusūf]. The sahābah were in agreement on not making takfīr of al-Hajjāj. It's confirmed in al-Bukhāri that ibn 'Umar prayed behind him. It's been reported that he said some munkar words but that is likely not authentic.

[تعليقات عل حاشية كتاب التوحيد لابن قاسم]

Sheikh al-Muhaddith 'Abdullah as-Sa'd (حفظه الله):

According to my knowledge, those who were the most correct in relating ijmā' (consensus) were Abu Muhammad ibn Hazm and Abu al-'Abbās ibn Taymiyyah; and the most lenient was Abu 'Umar ibn 'Abd al-Barr. Even ibn al-Mundhir was stricter than him (ibn 'Abd al-Barr), ibn 'Abd al Barr was more lenient. Muwaffaq ad-Dīn ibn Qudāmā also had leniency in relating ijmā'; likewise ibn al-Qayyim had leniency in relating ijmā'. However, ibn Hazm was among the strictest, and likewise ibn Taymiyyah.

[تعليقات على حاشية كتاب التوحيد لابن قاسم]

Sheikh 'Abdullah as-Sa'd (حفظه الله):

It is said that he (ibn 'Abd al-Hādi) was the most knowledgeable of the students of sheikh-ul-Islām [ibn Taymiyyah] in Hadīth, and it's been mentioned that ibn Muflih was the most knowledgeable of the students of sheikh-ul-Islām in fiqh, and ibn al-Qayyim was the most knowledgeable of the students of sheikh-ul-Islām in 'aqīdah and what relates to it.

[تعليقات على حاشية كتاب التوحيد لابن قاسم]

Sheikh 'Abdullah as-Sa'd (حفظه الله):

The most correct view is that the collection of ibn Hibban is more authentic than Sahih ibn Khuzayma, because ibn Khuzayma rahimahullah had leniency in narrating weak ahādīth that relate to fadhāil al-a'māl, particularly in the chapter of fasting in it's introduction he mentioned many weak ahādīth which are not sahīh, so ibn Hibban's book is more authentic; and the book of an-Nasāī is more authentic than [both of] these books; he often points out the defective ahādīth; if there is a defect in the hadīth he mentions the defect. Thus, many of the predecessors called an-Nasāī's book Sahīh an-Nasāī, as has been related from ibn 'Adī, and likewise from al-Khatīb al-Baghdādi, and also from Abu 'Abdillah al-Hākim, adh-Dhahabi, and others. And indeed most of the ahādīth of an-Nasāī (as-Sunan as-Sughrā) are Sahīh and the ahādīth which have defects he mentions the defects in these ahādīth.

[تعليقات على حاشية كتاب التوحيد لابن قاسم]

(Edit: some details [lines 4-9] have been added to the translation for more benefit which weren't included initially for the sake of summarisation)

Hadith benefit:

Sheikh al-Muhaddith 'Abdullah as-Sa'd (فك الله أسره) :

"In regard to Shabīb ibn Bishr al Bajali (hadith narrator), Yahya ibn Ma'īn declared him to be trustworthy, Abu Hātim ar-Rāzi said he is layyin (weak), while Ibn Hibban mentioned him in Kitāb ath-Thiqāt (book of trustworthy narrators) and said: 'he makes many mistakes'. What's most likely to be correct is that he (Shabīb) is hasan-al-hadīth (good narrator), la ba's bihi (no harm in him), sadūq (truthful but less precision).

Abu Hātim ar-Rāzi rahimahullah as we mentioned previously and as is well-known among many of those engrossed in hadīth sciences is that he is very strict (mutashaddid jiddan), and he barely ever declares a narrator to be trustworthy; to the point where he said about 'Abd ar-Razzaq, author of al-Musannaf, that his hadith is to be written down but isn't taken as a proof...while 'Abd ar-Razzaq is from the major huffādh...so he (Abu Hātim) rahimahullah is strict in declaring narrators to be trustworthy (shadīd-ut-tazkiyah).
So when his saying opposes the saying of Yahya ibn Ma'īn the saying of Yahya ibn Ma'īn is given preference over his since Yahya, even though he is a mutashaddid (strict), however his strictness is less [than Abu Hātim]; Yahya ibn Ma'in is closer than Abu Hātim to moderation (i'tidāl), so the saying of one who is mu'tadil (moderate) is given preference.

And it seems that ibn Hibban's criticism of Shabīb ibn Bishr would [only] lower him from the level of thiqqah to the level of sadūq since he [still] listed him in the book of thiqāt and didn't list him in the book of majrūhīn."

(The above is a summary of what the Sheikh stated as other less relevant details were discussed as well)

[تعليقات على حاشية كتاب التوحيد لابن قاسم]

Sheikh Abu Bakr al-Jazāiri رحمه الله (d. 2018 CE) in Nahr al Khayr, his commentary on his well-known tafsīr: Aysar-at-tafāsīr, said:

"The scholars have said that indeed whoever seeks other than the judgement of Allah ta'ālā, whereby he isn't pleased with it, is a kāfir; and this is the conditon of the Jews, and the condition of the majority of the Muslims today whereby they weren't pleased with the judgement of Allah ta'ālā; and they judged with the laws of falsehood and kufr."

Concerning āyah 55 of al-Māidah, the books of tafsīr mention a hadīth in which a beggar came to 'Ali ibn Abi Tālib while he was in rukū' and 'Ali took off his ring and gave him it, so based on that some thought that "...and they give zakāh, and they bow down" means giving zakāh while bowing and that it specifically refers to 'Ali رضي الله عنه.

Sheikh 'Abdullah as-Sa'd said "this hadith is bātil (false)."
And elsewhere he said "this hadīth is wāhī (weak)."

[Source: تأملات في سورة المائدة]

The Reason We Fight - Sheikh Khalid al Fulayj (فك الله أسره)

https://youtu.be/NbV7uysMLXs?feature=shared

Ahādīth on praying four rak'ah before Salāt-al-'Asr and their authenticity:

The hadīth narrated by ibn 'Umar رضي الله عنه that Prophet ﷺ said:
"May Allah show mercy to a man who prays four rak'ah before Salāt-al-'Asr" - Narrated by Abu Dawud and at-Tirmidhi

It is ma'lūl and not authentic according to Sh. Sulayman al-'Alwan, Sh. 'Abdullah as-Sa'd, Sh. Khalid al-Fulayj, and Sh. Mustafa al-'Adawi.


As for the hadith of Ali رضي الله عنه  that "Allah's Messenger ﷺ would pray four Rak'ah before Al-Asr separating between them by sending salam upon the angels that are close [to Allah] and those who follow them among the Muslims and the believers" Narrated by at-Tirmidhi

Sheikh 'Abdullah as-Sa'd  فك الله أسره said:
There is something [of doubt] within myself in regard to [authenticating] this hadith, during our reading of [Jāmi'] at-Tirmidhi I had said that this hadith is strong...but in fact [now] there is something [of doubt] within myself in regard to it, if there is an 'illa (hidden defect) in the report then it is 'Āsim bin Dhamrah...there are those who strengthened him and those who spoke [critically] about him...he was alone in mentioning this [report]. However, praying four rak'ah [salat nafilah] during the daytime [in general] is confirmed from some of the sahabah like ibn Mas'ūd and ibn 'Umar. (Summarised from his sharh of al Muharrar by ibn 'abd al-Hādi).

Sheikh Khalid al Fulayj فك الله أسره said:
Some of the huffādh considered this report defective due to 'Āsim bin Dhamrah such that some of them went so far as to say it is a bātil and fabricated hadith and that is due to 'Āsim being alone in narrating this report, as none of the other senior companions of 'Ali رضي الله عنه mentioned this report from 'Ali from the Prophet ﷺ, and this is considered an 'illa and nakārah by which this hadith is weakened. Having said that, we say that it's prescribed for one to pray two rak'ah before 'Asr due to the hadith "between every two adhān's there is a prayer...for whoever wishes" which comprises all of the prayers. And if one acted upon these ahādīth due to it being fadhail al-a'māl and that there is leniency in regard to weak ahādīth and he prayed four rak'ah before 'Asr then he will have the virtue mentioned in the hadīth of ibn 'Umar. (Summarised from his sharh of al Muharrar by ibn 'abd al-Hādi)

Sheikh Sulayman al-'Alwan فك الله أسره said: this sanad is strong, 'Asim bin Dhamrah is sadūq (truthful but less precise) and he has good narrations from 'Ali رضي الله عنه,  and this hadith it's sanad is strong, the like of it is used as proof, so it's recommended to pray four rak'ah before salāt-al-'Asr, and praying between the adhān and iqamah is prescribed in general due to the hadith "between every two adhān's there is a prayer...for whoever wishes" which is general for all times.

Sheikh Mustafa al-'Adawi said the hadith of 'Ali is ma'lūl, da'īf.

Summary: it's not authentic that the Prophet ﷺ verbally enjoined these four rak'ah; but as to whether he used to pray them himself or not, there are issues with it's authenticity; some authenticate it and some don't, however if one prays two or four or six rak'ah, or more than that, before 'Asr as nāfilah prayer there is no problem with that. والله أعلم .