Sunan Abi Dawud 1121
سنن أبي داود#1121SahihAbu Hurairah reported the Messenger of Allah (ﷺ) as saying:If anyone obtains a rak'ah in the prayer (along with the imam), he has obtained the whole prayer
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Muhyi Al-Din Abdul HamidSahih
Zubair Ali ZaiSahih Bukhari (580) Sahih Muslim (607)
In-book reference: 2:732