the Prophet said: "Whoever combines two prayers without any excuse then he has committed something from the major sins."
Jami` at-Tirmidhi Book 2, Hadith 40
← Previous Hadith "Allah's Messenger combined the Zuhr and Asr (prayers), and the Maghrib and Isha (prayers) in Al-Madinah, without being in a state of fear, nor due to rain."

Jami` at-Tirmidhi Book 2, Hadith 39 Next Hadith → "When we awoke, we went to Allah's Messenger to inform him of the dream. He said: 'Indeed this dream is true. So go to Bilal, for he has a better and louder voice than you. Convey to him what was said to you, so that he may call (to the prayer) with that.'" He said: "When Umar bin Al-Khattab heard Bilal calling for the prayer he went to Allah's Messenger, and he was dragging his Izar, (as he was hurrying) saying: 'O Allah's Messenger! By the One Who sent you with the truth! I dreamt the same as what he said.''' He said: "So Allah's Messenger said: 'To Allah is the praise, so that confirms it even more.'''

Jami` at-Tirmidhi Book 2, Hadith 41