Islamic territory. People would come to know Allah’s religion and its laws, and they would embrace it eagerly and of their own accord. At that point, O Messenger, you will have conveyed the message, fulfilled the trust, and carried out what Allah commanded you.

Nothing then remained save to seal this sublime act of worship with istighfar (seeking forgiveness), tasbih (declaring Allah’s transcendence), and preparation for meeting Allah, Exalted be He.

Accordingly, the Prophet ﷺ would repeat that formula often in his bowing and prostration, saying: “Subhanaka Allahumma Rabbana wa-bihamdik, Allahumma ighfir li” (“Glory be to You, O Allah, our Lord, and by Your praise; O Allah, forgive me”).

These words unite the affirmation that Allah is above every imperfection with an acknowledgment of His praises. After imploring Him through these majestic attributes, the servant then asks for forgiveness, for He is the Lord of piety and the Lord of forgiveness.

Rulings derived from the hadith

1. It is recommended to recite this supplication frequently during bowing and prostration.
2. Acts of worship—especially the prayer—should be concluded with istighfar so that any shortcomings therein may be remedied.
3. The most effective means of securing acceptance of supplication is to begin by praising Allah and declaring His transcendence above all defects and blemishes.
4. A worshipper who does so shows his concern for preserving his acts of devotion; therefore he should never feel secure from slips or deficiencies within them.
5. The virtue of seeking forgiveness and requesting it in every circumstance.
6. Shaykh al-Islam Ibn Taymiyyah noted that what is well known from Imam Ahmad is that he would not invoke in the prayer except with supplications transmitted from the Prophet. He understood the Prophet’s words, “thumma liyakhtar mina al-duʿāʾ mā shāʾ” (“then let him choose from supplications whatever he wishes”), to mean choosing from the prayers that have been reported in the texts. Thus, the recommended supplication is the one that is legislated. If, however, someone makes a supplication that is merely permissible and not known to be specifically recommended, his prayer is not invalidated. Indeed, something similar occurred with certain Companions during the Prophet’s lifetime and he did not censure them; he merely denied them the extra reward.

Benefit
Shaykh al-Islam Ibn Taymiyyah also said: As for the imam and the congregation making a collective supplication after the obligatory prayer, nothing has been transmitted indicating that the Prophet ﷺ ever did this at the conclusion of the prescribed prayers.