This Surah informs of the Completion of the Life of Allah's Messenger
Al-Bukhari recorded from Ibn Abbas that he said, "Umar used to bring me into the gatherings with the old men of (the battle of) Badr. However, it was as if one of them felt something in himself (against my attending). So he said,
`Why do you (`Umar) bring this (youth) to sit with us when we have children like him (i.e., his age)'
So `Umar replied, `Verily, he is among those whom you know.`
Then one day he called them and invited me to sit with them, and I do not think that he invited me to be among them that day except to show them. So he said,
`What do you say about Allah's statement,
إِذَا جَأءَ نَصْرُ اللَّهِ وَالْفَتْحُ
(When there comes the help of Allah and the Conquest.)'
Some of them said,
`We were commanded to praise Allah and seek His forgiveness when He helps us and gives us victory.'
Some of them remained silent and did not say anything.
Then he (Umar) said to me, `Is this what you say, O Ibn `Abbas'
I said, `No.'
He then said, `What do you say'
I said,
`It was the end of the life of Allah's Messenger that Allah was informing him of.
Allah said,
إِذَا جَاء نَصْرُ اللَّهِ وَالْفَتْحُ
When there comes the help of Allah and the Conquest.
which means, that is a sign of the end of your life.
فَسَبِّحْ بِحَمْدِ رَبِّكَ وَاسْتَغْفِرْهُ إِنَّهُ كَانَ تَوِبَا
So, glorify the praises of your Lord, and ask His forgiveness. Verily, He is the One Who accepts the repentance and Who forgives.'
So, Umar bin Al-Khattab said,
`I do not know anything about it other than what you have said."'
Al-Bukhari was alone in recording this Hadith.
Imam Ahmad recorded from Ibn Abbas that he said,
"When
إِذَا جَأءَ نَصْرُ اللَّهِ وَالْفَتْحُ
(When there comes the help of Allah and the Conquest.) was revealed, the Messenger of Allah said,
نُعِيَتْ إِلَيَّ نَفْسِي
My death has been announced to me. And indeed he died during that year."
Ahmad was alone in recording this Hadith.
Al-Bukhari recorded that Aishah said,
"The Messenger of Allah used to say often in his bowing and prostrating,
سُبْحَانَكَ اللَّهُمَّ رَبَّنَا وَبِحَمْدِكَ اللَّهُمَّ اغْفِرْ لِي
(Glory to You, O Allah, our Lord, and praise be to You. O Allah, forgive me.) He did this as his interpretation of the Qur'an (i.e., showing its implementation)."
The rest of the group has also recorded this Hadith except for At-Tirmidhi.
Imam Ahmad recorded from Masruq that Aishah said,
"The Messenger of Allah used to often say towards the end of his life,
سُبْحَانَ اللهِ وَبِحَمْدِهِ أَسْتَغْفِرُ اللهَ وَأَتُوبُ إِلَيْه
Glory to Allah, and praise be unto Him. I seek Allah's forgiveness and I repent to Him.
And he said,
إِنَّ رَبِّي كَانَ أَخْبَرَنِي أَنِّي سَأَرَى عَلَمَةً فِي أُمَّتِي وَأَمَرَنِي إِذَا رَأَيْتُهَا أَنْ أُسَبِّحَ بِحَمْدِهِ وَأَسْتَغْفِرَهُ إِنَّهُ كَانَ تَوَّابًا فَقَدْ رَأَيْتُهَا
إِذَا جَأءَ نَصْرُ اللَّهِ وَالْفَتْحُ
وَرَأَيْتَ النَّاسَ يَدْخُلُونَ فِي دِينِ اللَّهِ أَفْوَاجًا