He who observed prayer at night during Ramadan, because of faith and seeking his reward from Allah, his previous sins would be forgiven.  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ مَنْ قَامَ رَمَضَانَ إِيمَانًا وَاحْتِسَابًا غُفِرَ لَهُ مَا تَقَدَّمَ مِنْ ذَنْبِهِ  

The Messenger of Allah ﷺ used to exhort (his Companions) to pray (at night) during Ramadan without commanding them to observe it as an obligatory act, and say: He who observed the night prayer in Ramadan because of faith and seeking his reward (from Allah), all his previous sins would be forgiven. When Messenger of Allah ﷺ died, this was the practice, and it continued thus during Abu Bakr's caliphate and the early part of 'Umar's caliphate.  

كَانَ رَسُولُ اللَّهِ ﷺ يُرَغِّبُ فِي قِيَامِ رَمَضَانَ مِنْ غَيْرِ أَنْ يَأْمُرَهُمْ فِيهِ بِعَزِيمَةٍ فَيَقُولُ مَنْ قَامَ رَمَضَانَ إِيمَانًا وَاحْتِسَابًا غُفِرَ لَهُ مَا تَقَدَّمَ مِنْ ذَنْبِهِ فَتُوُفِّيَ رَسُولُ اللَّهِ ﷺ وَالأَمْرُ عَلَى ذَلِكَ ثُمَّ كَانَ الأَمْرُ عَلَى ذَلِكَ فِي خِلاَفَةِ أَبِي بَكْرٍ وَصَدْرًا مِنْ خِلاَفَةِ عُمَرَ عَلَى ذَلِكَ  

He who observed the fasts of Ramadan with faith and seeking reward (from Allah), all his previous sins would be forgiven, and he who observed prayer on Lailat-ul- Qadr with faith and seeking reward (from Allah), all his previous sins would be forgiven.  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ مَنْ صَامَ رَمَضَانَ إِيمَانًا وَاحْتِسَابًا غُفِرَ لَهُ مَا تَقَدَّمَ مِنْ ذَنْبِهِ وَمَنْ قَامَ لَيْلَةَ الْقَدْرِ إِيمَانًا وَاحْتِسَابًا غُفِرَ لَهُ مَا تَقَدَّمَ مِنْ ذَنْبِهِ  

He who prayed on the Lailat-ul-Qadr (the Majestic Night) knowing that it is (the same night). I (believe) that he (the Prophet also) said: (He who does) it with faith and seeking reward (from Allah), his sins would be forgiven.  

عَنِ النَّبِيِّ ﷺ قَالَ مَنْ يَقُمْ لَيْلَةَ الْقَدْرِ فَيُوَافِقُهَا أُرَاهُ قَالَ إِيمَانًا وَاحْتِسَابًا غُفِرَ لَهُ  

I saw what you were doing, but I desisted to come to you (and lead the prayer) for I feared that this prayer might become obligatory for you. (He the narrator) said: It was the month of Ramadan.  

أَنَّ رَسُولَ اللَّهِ ﷺ صَلَّى فِي الْمَسْجِدِ ذَاتَ لَيْلَةٍ فَصَلَّى بِصَلاَتِهِ نَاسٌ ثُمَّ صَلَّى مِنَ الْقَابِلَةِ فَكَثُرَ النَّاسُ ثُمَّ اجْتَمَعُوا مِنَ اللَّيْلَةِ الثَّالِثَةِ أَوِ الرَّابِعَةِ فَلَمْ يَخْرُجْ إِلَيْهِمْ رَسُولُ اللَّهِ ﷺ فَلَمَّا أَصْبَحَ قَالَ قَدْ رَأَيْتُ الَّذِي صَنَعْتُمْ فَلَمْ يَمْنَعْنِي مِنَ الْخُرُوجِ إِلَيْكُمْ إِلاَّ أَنِّي خَشِيتُ أَنْ تُفْرَضَ عَلَيْكُمْ قَالَ وَذَلِكَ فِي رَمَضَانَ  

The Messenger of Allah ﷺ came out during the night and observed prayer in the mosque and some of the people prayed along with him. When it was morning the people talked about this and so a large number of people gathered there. The Messenger of Allah ﷺ went out for the second night, and they (the people) prayed along with him. When it was morning the people began to talk about it. So the mosque thronged with people on the third night. He (the Holy Prophet) came out and they prayed along with him. When it was the fourth night, the mosque was filled to its utmost capacity but the Messenger of Allah ﷺ did not come out. Some persons among then cried:" Prayer." But the Messenger of Allah ﷺ did not come to them till he came out for the morning prayer. When he had completed the morning prayer, he turned his face to the people and recited Tashahhud (I bear testi- mony that there is no god but Allah and I bear testimony that Muhammad is His Messen- ger) and then said: Your affair was not hidden from me in the night, but I was afraid that (my observing prayer continuously) might make the night prayer obligatory for you and you might be unable to perform it.  

أَنَّ رَسُولَ اللَّهِ ﷺ خَرَجَ مِنْ جَوْفِ اللَّيْلِ فَصَلَّى فِي الْمَسْجِدِ فَصَلَّى رِجَالٌ بِصَلاَتِهِ فَأَصْبَحَ النَّاسُ يَتَحَدَّثُونَ بِذَلِكَ فَاجْتَمَعَ أَكْثَرُ مِنْهُمْ فَخَرَجَ رَسُولُ اللَّهِ ﷺ فِي اللَّيْلَةِ الثَّانِيَةِ فَصَلَّوْا بِصَلاَتِهِ فَأَصْبَحَ النَّاسُ يَذْكُرُونَ ذَلِكَ فَكَثُرَ أَهْلُ الْمَسْجِدِ مِنَ اللَّيْلَةِ الثَّالِثَةِ فَخَرَجَ فَصَلَّوْا بِصَلاَتِهِ فَلَمَّا كَانَتِ اللَّيْلَةُ الرَّابِعَةُ عَجَزَ الْمَسْجِدُ عَنْ أَهْلِهِ فَلَمْ يَخْرُجْ إِلَيْهِمْ رَسُولُ اللَّهِ ﷺ فَطَفِقَ رِجَالٌ مِنْهُمْ يَقُولُونَ الصَّلاَةَ فَلَمْ يَخْرُجْ إِلَيْهِمْ رَسُولُ اللَّهِ ﷺ حَتَّى خَرَجَ لِصَلاَةِ الْفَجْرِ فَلَمَّا قَضَى الْفَجْرَ أَقْبَلَ عَلَى النَّاسِ ثُمَّ تَشَهَّدَ فَقَالَ أَمَّا بَعْدُ فَإِنَّهُ لَمْ يَخْفَ عَلَىَّ شَأْنُكُمُ اللَّيْلَةَ وَلَكِنِّي خَشِيتُ أَنْ تُفْرَضَ عَلَيْكُمْ صَلاَةُ اللَّيْلِ فَتَعْجِزُوا عَنْهَا  

I heard from Ubayy b. Ka'b a statement made by 'Abdullah b. Mas'ud in which he said: He who gets up for prayer (every night) during the year will hit upon Lailat-ul-Qadr. Ubayy said: By Allah I there is no god but He, that (Lailat-ul-Qadr) is in Ramadhan (He swore without reservation: ) By Allah, I know the night; it is the night on which the Messenger of Allah ﷺ commanded us to pray. It is that which precedes the morning of twenty-seventy and its indication is that the sun rises bright on that day without rays.  

أُبَىٌّ وَاللَّهِ الَّذِي لاَ إِلَهَ إِلاَّ هُوَ إِنَّهَا لَفِي رَمَضَانَ يَحْلِفُ مَا يَسْتَثْنِي وَوَاللَّهِ إِنِّي لأَعْلَمُ أَىُّ لَيْلَةٍ هِيَ هِيَ اللَّيْلَةُ الَّتِي أَمَرَنَا بِهَا رَسُولُ اللَّهِ ﷺ بِقِيَامِهَا هِيَ لَيْلَةُ صَبِيحَةِ سَبْعٍ وَعِشْرِينَ وَأَمَارَتُهَا أَنْ تَطْلُعَ الشَّمْسُ فِي صَبِيحَةِ يَوْمِهَا بَيْضَاءَ لاَ شُعَاعَ لَهَا  

By Allah, I know about Lailat-ul Qadr and I know it fully well that it is the twenty-seventh night (during Ramadan) on which the Messenger of Allah ﷺ commanded us to observe prayer. (Shu'ba was in doubt about these words:" the night on which the Messenger of Allah [may peace be upon him] commanded us to observe the prayer." This has been transmitted to me by a friend of mine.)  

أُبَىٌّ فِي لَيْلَةِ الْقَدْرِ وَاللَّهِ إِنِّي لأَعْلَمُهَا وَأَكْثَرُ عِلْمِي هِيَ اللَّيْلَةُ الَّتِي أَمَرَنَا رَسُولُ اللَّهِ ﷺ بِقِيَامِهَا هِيَ لَيْلَةُ سَبْعٍ وَعِشْرِينَ وَإِنَّمَا شَكَّ شُعْبَةُ فِي هَذَا الْحَرْفِ هِيَ اللَّيْلَةُ الَّتِي أَمَرَنَا بِهَا رَسُولُ اللَّهِ ﷺ قَالَ وَحَدَّثَنِي بِهَا صَاحِبٌ لِي عَنْهُ  

Shu'ba reported this hadith with the same chain of transmitters, but he made no mention that Shu'ba was in doubt and what follows subsequently.  

حَدَّثَنَا شُعْبَةُ بِهَذَا الإِسْنَادِ نَحْوَهُ وَلَمْ يَذْكُرْ إِنَّمَا شَكَّ شُعْبَةُ وَمَا بَعْدَهُ