Sunan an Nasai
1443
Sahih+2

It was narrated that Qatadah said:"I heard Muas- bin Salamah-say: 'I said to Ibn 'Abbas: How should I pray in Makkah if I do not pray in congregation? He said: Two rak'ahs, the sunnah of Abu Al-Qasim

SahihAbu Ghuddah
SahihAl-Albani