Jami` at-Tirmidhi 176
جامع الترمذي#176SahihAbu Dharr narrated that :the Prophet said: "O Abu Dharr! There will be leaders after me who cause the Salat to die; so perform the Salat during its time. If you pray (with them) during its time, then that will be voluntary Salat for you, if not, then you will have attained your Salat
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 ZaiSahih Muslim
In-book reference: 2:28