Sunan Abi Dawud 927
سنن أبي داود#927SahihNarrated Abdullah ibn Umar: The Messenger of Allah (ﷺ) went to Quba to offer prayer. Then the Ansar (the Helpers) came to him and gave him a salutation while he was engaged in prayer. I asked Bilal: How did you find the Messenger of Allah (ﷺ) responding to them when they gave him a salutation while he was engaged in prayer. He replied: In this way, and Ja'far ibn Awn demonstrated by spreading his palm, and keeping its inner side below and its back side above
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniHasan Sahih
Muhammad Muhyi Al-Din Abdul HamidHasan Sahih
Shuaib Al ArnautHasan
Zubair Ali ZaiSahih
In-book reference: 2:538