Jami` at-Tirmidhi 238
جامع الترمذي#238Da'ifAbu Sa'eed narrated that :Allah's Messenger said: "the key to Salat is the purification, its Tahrim is the Takbir, and its Tahlilis the Taslim, and there is no Salat for one who did not recite Al-Hamd and a Surah in the obligatory (prayer) or other prayers
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
Zubair Ali ZaiDaif
In-book reference: 2:90