Chapter: It is recommended to greet the masjid by praying two rak`ah, and it is disliked to sit before praying these two rak`ah, and this is prescribed at all times

When any one of you enters the mosque, he should observe two rak'ahs (of Nafl prayer) before sitting.

I entered the mosque, when the Messenger of Allah (ﷺ) had been sitting among people, and I also sat down among them. Upon this the Messenger of Allah (ﷺ) said: What prevented you from offering two rak'ahs (of Nafl prayer) before sitting down? I said: Messenger of Allah, I saw you sitting and people sitting (around you and I, therefore, sat in your company). He (the Holy Prophet) then said: When anyone among you enters the mosque, he should not sit till he has observed two rak'ahs.

The Apostle of Allah (ﷺ) owed me a debt; he paid me back and made an addition (of this). I entered the mosque and he (the Holy Prophet) said to me: Observe two rak'ahs of prayer.