Jami` at-Tirmidhi 808
جامع الترمذي#808SahihAbu Hurairah narrated:"The Messenger of Allah would encourage the night prayer in Ramadan without firmly ordering it, and he would say: "Whoever stands (in the night prayer) for Ramadan with faith and seeking the reward (from Allah), then he will be forgiven what has preceded of his sins.' So the Messenger of Allah died and the matter was like that. Then the matter was the same during the Khilafah of Abu Bakr and it continued during a portion of the Khilafah of Umar bin Al-Khattab
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Ahmad Muhammad ShakirSahih
Al-AlbaniSahih
Bashar Awad MaaroufHasan Sahih
Zubair Ali ZaiSahih Muslim
In-book reference: 8:127