Jami` at-Tirmidhi 3734
جامع الترمذي#3734Da'ifNarrated Ibn 'Abbas:"The first to perform Salat was 'Ali
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Ahmad Muhammad ShakirSahih
Al-AlbaniDaif
Zubair Ali ZaiHasan
In-book reference: 49:131