Sunan Abi Dawud Book 5, Hadith 21
The Prophet (ﷺ) said: The gates of heaven are opened for four rak'ahs containing no taslim (salutation) before the noon prayer.
Abu Dawud said: Yahya b. Sa'id al-Qattan said: If I were to narrate any tradition from 'Ubaidah, I would narrate this tradition.
Abu Dawud said: 'Ubaidah is weak.
Abu Dawud said: The name of the narrator Ibn Minjab is Sahm.
The Prophet (ﷺ) said: If anyone keeps on praying regularly four rak'ahs before and four after the noon prayer, he will not enter the Hell-fire.
Abu Dawud said: Al-'Ala' bin Al-Harith and Sulaiman bin Musa reported it from Makhul with his chain, similarly.
The Prophet (ﷺ) said: May Allah show mercy to a man who prays four rak'ahs before the afternoon prayer.