I once heard him raise it as a marfu report, then he stopped doing so. He saw a commander, or a man, give the salam twice, so he said, "Where did he pick that up from?"
حدثنا يحيى عن شعبة عن الحكم عن مجاهد عن أبي معمر
سمعته مرة رفعه ثم تركه رأى أميرا أو رجلا سلم تسليمتين فقال أنى علقها
Its isnad is sahih. Muslim narrated it (1:162) from Ahmad bin Hanbal, and Bayhaqi likewise narrated it (3:176) through the route of the Musnad. This is a brief narration condensed into a single sentence, which is clarified also by Muslim's narration, from Zuhayr bin Harb, from Yahya bin Saeed, from Shubah, from Hakam and Mansur, from Mujahid, from Abu Muamar, that a governor in Makkah used to give the salam twice, so Abdullah said, "Where did he pick this up from?" Hakam said in his version of the hadith, "The Messenger of Allah ﷺ used to do it."The meaning of Ibn Masud's statement, "Where did he pick this up from?" is "From where did he take it and learn it?" In manuscript H it reads "I picked it up," and in manuscript K it reads "I did it." We have adopted what appears in the marginal copy of manuscript K, since it agrees with what is in Sahih Muslim. See 4172.