Sunan an-Nasa'i 534
سنن النسائي#534Da'ifIt was narrated from Abu Hurairah that the Messenger of Allah (ﷺ) said:"Were it not that I would impose too much difficulty on my Ummah, I would have commanded them to delay 'Isha' and to use the Siwak for every prayer
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih
Al-AlbaniDaif
Zubair Ali ZaiSahih Muslim
In-book reference: 6:41