Unbasa bin Abi Sufyan · The Book on Salat (Prayer)

"Whoever is regular with twelve Rak'ah of Sunnah (prayer), Allah will build a house for him in Paradise: Four Rak'ah before Zuhr, two Rak'ah after it, two Rak'ah after Maghrib, two Rak'ah after Isha, and two Rak'ah before Fajr."

"When the Prophet (S) would not perform the four Rak'ah before Az-Zuhr he would pray them after it."

Allah's Messenger (S) said: "Whoever prays four before Az-Zuhr and four after, Allah makes him prohibited for the Fire."