[The Best Supplication, the Best Remembrance, and the Best Times for an Answer]

The answer—and Allah is the One Who grants success and assistance —is that the best supplication is seeking forgiveness, as evidenced by what Allah—Blessed and Exalted—related of the faith of the Messenger (May Allah bless him and his family and grant them peace) and the believers at the end of Surah Al-Baqarah; so the first of their supplication after mentioning faith was their saying: "Our forgiveness, our Lord, and to You is the return" [Al-Baqarah:285]. And Allah—Exalted is He—related the supplication of Nūḥ (Peace be Upon Him): "My Lord, forgive me and my parents and whoever enters my house as a believer and the believing men and the believing women. And do not increase the wrongdoers except in destruction" [Nuh:28]; and the supplication of Mūsā: "My Lord, forgive me and my brother" [Al-A‘raf:151]. And Allah praised the people of understanding, so He—Exalted is He—said: "Those who say, 'Our Lord, indeed we have believed, so forgive us our sins and protect us from the punishment of the Fire'—the patient, the truthful, the devoutly obedient, the spenders, and those who seek forgiveness in the pre-dawn hours" [Aal ‘Imran:16–17]. And He—Exalted is He—said: "They used to sleep but little of the night, and in the pre-dawn hours they would seek forgiveness" [Adh-Dhariyat:17–18].
And He commanded His Prophet (May Allah bless him and his family and grant them peace), saying: "And ask forgiveness for your sin and for the believing men and the believing women" [Muhammad:19] … "So glorify the praise of your Lord and ask His forgiveness" [An-Nasr:3]. And He—Exalted is He—said: "Indeed, there was a group of My servants who used to say, 'Our Lord, we have believed, so forgive us and have mercy upon us, and You are the best of the merciful'" [Al-Mu’minun:109]. And Allah—Exalted is He—mentioned the supplication of the angels, saying: "Those who carry the Throne and those around it glorify the praise of their Lord and believe in Him and ask forgiveness for those who have believed: 'Our Lord, You have encompassed all things in mercy and knowledge, so forgive those who have repented…'" [Ghafir:7]. And Allah—Exalted is He—mentioned the supplication of the believers for their brothers who preceded them: "Our Lord, forgive us and our brothers who preceded us in faith…" [Al-Hashr:10]—and other than that which Allah—Exalted is He—related in His Noble Book of supplication; for you find that most of it and the majority of it is supplication for forgiveness, which indicates its superiority over other supplications.
This is so; and what we said is supported from the standpoint of reflection: that seeking forgiveness—if it is as it should be—comprises several matters, in each of which there is magnifying Allah and venerating Him. For seeking forgiveness—true seeking forgiveness—has behind it the sense and feeling of falling short in obeying Allah, and neglect in His remembrance and gratitude, and shortcoming in mentioning His blessings, and forgetfulness of sins, and failing to establish what Allah commanded of His obligations with their due establishment because of the abundance of distracting whispers in prayer and the like. And that the blessings of Allah—Exalted is He—are many: how many of Allah’s blessings upon him has he not mentioned and not thanked for; and how many a blessing passed over him while he was heedless. And that no matter how far he reaches in piety toward Allah, he is still falling short in the right of Allah, in need of His forgiveness and His mercy.
So bringing to mind such matters as we mentioned is a great act of worship of Allah—Exalted is He—and perhaps it and what resembles it is the greatest remembrance of Allah referred to in His—Exalted is He—saying: "… and the remembrance of Allah is greater …" [Al-‘Ankabut:45].
And what we mentioned is supported by the fact that seeking forgiveness gathers the good of this world and the Hereafter, as evidenced by His—Exalted is He—saying: "So I said, 'Ask forgiveness of your Lord. Indeed, He is ever a Perpetual Forgiver. He will send the sky upon you in [continuing] showers, and give you increase in wealth and children, and provide for you gardens and provide for you rivers'" [Nuh: 10–12], and His—Exalted is He—saying: "Indeed, the righteous will be among gardens and springs, taking what their Lord has given them. Indeed, they were before that doers of good. They used to sleep but little of the night, and in the pre-dawn hours they would seek forgiveness" [Adh-Dhariyat:15–18]. And in this verse is evidence that the best times for seeking forgiveness are the pre-dawn hours.
This is so; as for the best remembrance, it is as is narrated: “Glory be to Allah, and praise be to Allah, and there is no god but Allah, and Allah is the Greatest, and there is no power and no might except by Allah, the Most High, the Most Great,” and: “There is no god but Allah alone, with no partner; to Him belongs the dominion and to Him belongs praise; He gives life and causes death; in His hand is all good, and He is Powerful over all things.”
This is so; and the best remembrance may be what Allah—Exalted is He—legislated in the prayer, and the evidence for that is that the prayer is the best of deeds, and remembrance is a part of it; and based on this, the best remembrance is: reciting Surah Al-Fatihah, the takbīr, the glorification in bowing and prostration, “Glory be to Allah, praise be to Allah, there is no god but Allah, and Allah is the Greatest,” the two testimonies, and sending blessings upon the Prophet and his family (May Allah bless him and his family and grant them peace).

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