Sunan Abi Dawud 925
سنن أبي داود#925SahihNarrated Suhayb: I passed by the Messenger of Allah (ﷺ) who was praying. I saluted him and he returned it by making a sign. The narrator said: I do not know but that he said: He made a sign with his finger. This is the version reported by Qutaybah
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
In-book reference: 2:536