Sahih al-Bukhari Book 10, Hadith 56
The Prophet (ﷺ) said, "Allah will prepare for him who goes to the mosque (every) morning and in the
afternoon (for the congregational prayer) an honorable place in Paradise with good hospitality for
(what he has done) every morning and afternoon goings.
Anas was asked, "Did Allah's Messenger (ﷺ) wear a ring?" He said, "Yes. Once he delayed the `Isha' prayer till midnight and after the prayer, he faced us and said, 'The people prayed and have slept and you remained in prayer as long as you waited for it.' " Anas added, "As if I were just now observing the glitter of his ring."
Allah's Messenger (ﷺ) passed by a man praying two rak`at after the Iqama (had been pronounced). When Allah's Messenger (ﷺ) completed the prayer, the people gathered around him (the Prophet) or that man and Allah's Messenger (ﷺ) said to him (protesting), Are there four rak`at in Fajr prayer? Are there four rak`at in Fajr prayer?"