ENOfficial
Abu Qatada reported God’s Messenger as saying, “When one of you enters the mosque he should pray two rak'as before sitting down.” (Bukhari and Muslim.)
Source: sunnah.com
Other translations
Arabic
وَعَنْ أَبِي قَتَادَةَ أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «إِذَا دَخَلَ أَحَدُكُمُ الْمَسْجِدَ فَلْيَرْكَعْ رَكْعَتَيْنِ قَبْلَ أَنْ يجلس»
sunnah.com