[The Best Supplication and the Best Remembrance After the Qur’an]

Answer—and Allah is the One Who grants success: What appears to me is that the best supplication is what Allah—Exalted is He—has mentioned in the Qur’an. And most of the supplication mentioned in the Qur’an on the tongues of the prophets and the righteous is seeking forgiveness; and in it there is much urging to seek forgiveness frequently. And after seeking forgiveness in abundance is seeking mercy; and very often, in the Qur’an, the mention of forgiveness and mercy comes together.
And in the Qur’an there is much supplication, but it is not in abundance like seeking forgiveness and mercy. Among that is seeking repentance; among it is seeking protection from the Fire and from disgrace; and seeking Paradise: "And make me among the inheritors of the Paradise of bliss" [Ash-Shu‘ara’:85]; and seeking knowledge and wisdom; and supplicating for the righteousness of offspring and spouse; and seeking death upon Islam; and supplicating to join the righteous; and seeking patience and steadfastness; and victory over the disbelieving people; and seeking safety from the trial of the wrongdoing and disbelieving people, and seeking deliverance from them; and seeking steadfastness upon guidance: "Our Lord, do not let our hearts deviate" [Aal ‘Imran:8]; "Guide us to the straight path" [Al-Fatihah:1].
And in it is the mention of seeking elevation in His—Exalted is He—saying: "And make us an example for the righteous" [Al-Furqan:74]; and in His—Exalted is He—saying: "And grant me a reputation of truth among later generations" [Ash-Shu‘ara’:84].
And in it is the mention of seeking provision, and seeking guardianship and support in His—Exalted is He—saying: "And appoint for us from Yourself a protector, and appoint for us from Yourself a helper" [An-Nisa’:75]; and: "And appoint for me a minister from my family—Harun, my brother" [Ta-Ha].
And in it is seeking refuge for the supplicant and his offspring from Satan, the accursed; and: "… and from the evil of what He created … and from the evil of the whisperer …"—the sūrah.
And in it is the mention of supplication against the wrongdoers, and the supplication for safety from accompanying them and from following their way: "Not of those who have earned [Your] anger …" [Al-Fatihah: 7].
And in it is the mention of seeking the good of this world and the Hereafter in His saying: "Our Lord, grant us in this world …" [Al-Baqarah].
And in it is the command to send prayers and peace upon the Prophet (May Allah bless him and his family and grant them peace); and in it … and in it … etc.
As for the remembrance that Allah—Exalted is He—has mentioned in the Qur’an, it is glorification, praise, and magnification; and there has come the command for remembrance in absolute terms.
And the best remembrance is what Allah—Exalted is He—has mentioned of Himself; that is like Āyat al-Kursī, al-Fātiḥah, al-Ikhlāṣ, and the endings of Sūrat al-Ḥashr; and: "Say, O Allah, Owner of sovereignty …" [Aal ‘Imran:26]; and: "And say: Praise be to Allah, who has not taken a son …" [Al-Isra’:111]; and what He—Exalted is He—relayed from His prophets (Peace be Upon Them), like His—Exalted is He—saying: "Our Lord, indeed You know what we conceal and what we declare …" [Ibrahim: 3]; and: "There is no god except You; glory be to You; indeed, I have been among the wrongdoers" [Al-Anbiya’:87];
and the like of: "Our Lord, You did not create this in vain; glory be to You" [Aal ‘Imran:191]; and: "Our Lord, You have encompassed all things in mercy and knowledge" [Ghafir: 7].
Yes, it may be that the best supplication and remembrance is what Allah—Exalted is He—legislated in the prayer: that is, the takbīr, and reciting al-Fātiḥah, and saying “Allah hears the one who praises Him,” and praising for the one following the imam, and the glorification of bowing and prostration, and the tashahhud and sending prayers upon the Prophet (May Allah bless him and his family and grant them peace), and saying “Glory be to Allah, praise be to Allah, there is no god but Allah, and Allah is the Greatest” in the last two rak‘ahs.

Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.3