Imam Ahmed Riđā acknowledges this (in the book: Walidayn e Mustafa) and then says: 'If it is a mistake to consider them Muslims, it is better to commit an error on the side of caution and for the sake of love and adab; than making a mistake that is opposed to love and adab.'

Imām Suyūţi writes in his book ‘Masālik al-Ĥunafā’ quoting Imām Fakhruddīn Rāzī’s tafsīr ‘Asrār at-Tanzīl’: “Therefore the verse proves that all the ancestors of Muĥammad şallAllāhu álayhi wa sallam were muslims; it becomes necessary then, that the father of [sayyidunā] Ibrāhīm was not a kāfir. Rather he [āzar mentioned in the qur’ān] was his paternal uncle.

Even if the verse: ‘wa taqallubaka fi’s sājidīn’ / and we shall pass you on amongst the sājids [worshippers of Allāh; Surah ash-Shuárā’a, v.219] is explained in other ways, and even if all the reports [of ancestors not being muslims] are posited – no one can deny that this one verse supersedes them all. And if the meaning of this verse is established [as above], it follows that it is proof that the father of Ibrāhīm was not a polytheist.

Among things that establish that the parents of Muĥammad şallAllāhu álayhi wa sallam were not polytheists [mushrikīn] is the Ĥadīth: ‘I have always been passed on from pure fathers [*] to pure wombs’ and Allāh subĥānahu wa táālā says: “innama’l mushrikūna najas” / verily, the polytheists are impure, dirty. [Surah at-Tawbah, v.28] Therefore, it becomes necessary that none of his ancestors were polytheists.

*aşlāb, plural of şulb means the spine or the vertebral column, but used to indicate fatherhood just as womb indicates motherhood.

Hāfiž Ibn Nāşiruddīn Dimashqī says:

tanaqqala aĥmadu nūran ážīmā
tal’ala’a fī jibāhi’s sājidīnā
taqallaba fīhim qarnan fa qarnā
ilā an jā’a khayru’l mursalīnā

The great light (nūr) of Ahmed was being passed on,
Which shone in the foreheads of the prostrating ones [sājidīn]
And from them it kept changing for centuries,
Until he came to us as the best of all messengers.

He also says regarding the Ĥadīth of RasūlAllāh şallAllāhu álayhi wa sallam bringing his parents back to life and their becoming mu’mins:

ĥubbani’llāhi’n nabiyya mazīda fađlin
álā fađlin wa kāna bihī Ra’ūfā
fa aĥyā ummahū wa kadha abāhū
li īmānin bihī fađlan laţīfā
fa sallim fa’l Qadīmu bi dhā Qadīrin
wa in kāna’l ĥadīthu bihī đaýīfā

Because of Allah's love for His prophet and to increase His bounty,
Among bounties aplenty, and that He loves him;
Brought back to life, his mother and his father,
To profess their faith, is a more subtler gift [than being just muslims/ahl al-fitrah]
Accept it! because, al-Qadīm [the Eternal] has the Power to do it;
Even if the report of such an occurrence is a weak one.

In his ‘Al-Maqālatu’s Sundusiyyah’, Suyūţi takes Sakhāwi to task for apparently having a contrary view; for saying that ‘Both [parents] are in hellfire’. [though he mentions him as : ‘a scholar of ĥadīth’, he does mention his name twice in couplets running with the text] At this Suyūţi explodes; and is as eloquent as incisive in his refutation.

“…and let him spend all his energies to [prove it] if he is capable enough. When his reach falls short, and his knowledge reaches its limit, he extends his tongue and doles out abuses and insults. We belong to Allāh; there no strength nor power except granted by Allāh.

…if he wishes me to revise the opinion which I have preferred, [meaning Islām of RasūlAllāh’s şallAllāhu álayhi wa sallam parents] even if I am shred to pieces I shall not repeal my judgement. And I intend not from it [being steadfast] except for siding with the right.”

Discussing ahl al-fitrah or those who passed away before the message of RasūlAllāh şallAllāhu álayhi wa sallam, he says: “It is reported from a rigorously authenticated ĥadīth that Abū Ţālib faces the least torment in hell because of his relation [to RasūlAllāh SallAllāhu `alayhi wa sallam] and his kindness and aid [to RasūlAllāh SallAllāhu `alayhi wa sallam]. This is after his having lived for a very long time [after the announcement of Islam] and refusing allegiance to his command.

“…and how does this compare with his parents’ case: who are much closer in relation [than Abū Ţālib], certainly, of much more affection; who lived shorter, and have an excuse far better – we seek Allāh’s refuge – that they be in ranks of hell, and to them a great torment befell; anyone with sanity cannot understand this vanity.”

و قد صح في أبي طالب أنه أهون أهل النار عذابا – لما حازه من بره وقرابته اقترابا – هذا مع امتداد عمره – وامتناعه من طاعة أمره – فما ظنك بأبويه الذين هما أشد قربا – وآكد حبا – وأقصر عمرا – وأبسط عذرا – فمعاذ الله! أن يكونا في طبقة الجحيم – و أن يشتد العذاب العظيم – هذا لا يفهمه من له أدنى ذوق سليم

Imām Suyūţi’s monographs on the subject:

1. Al-Maqāmatu’s Sundusiyyah fi’n Nisbati’l Muşţafawiyyah

2. Ad-Daraj al-Munīfah fī Ābāyihi’sh Sharīfah
3. Masālik al-Hunafā fī Wāliday al-Muşţafā
4. Nashr al-Álamayn al-Munīfayn fī Iĥyāyi’l Abawayn ash-Sharīfayn
5. At-Tážīmu wa’l Minnah fī Anna Abaway Rasūlullāhi fi’l Jannah
6. As-Subul al-Jalīyyah fi’l Ābāyi’l Áliyyah

These are included in the seventy nine monographs of Imām Suyūţi that form two volumes of “Al-Hāwī li’l Fatāwī”. The six mentioned above, along with four others below were printed by Dār Kutub al-Ílmiyyah in one volume titled: “Ar-Rasāyil al-Áshar”:

7. Tanzīhi’l Anbiyā’a án Tashbīhi’l Aghbiyā’a

8. Inbāu’l Azkiyā’a fī Ĥayāti’l Anbiyā’a
9. Al-Árf al-Wardī fī Akhbār al-Mahdī
10. Tabyīđ aş-Şaĥīfah fī Manāqibi’l Imām Abī Ĥanīfah