Ikrama عكرمة · The Book on Salat (Prayer)

the Prophet said: "Whoever combines two prayers without any excuse then he has committed something from the major sins."

"Allah's Messenger performed Salat on a Khumrah."

"We were with the Prophet (S) on a journey when it started to rain on us, so the Prophet (S) said: 'Whoever wishes, let him perform Salat in his place.'"