Is it permissible to combine prayers without an excuse? And did the Prophet (peace be upon him) pray the five daily prayers at their prescribed times, or did he combine them? And what is the evidence for that?

What is constant and successively transmitted from the actions of the Prophet, peace and blessings be upon him, and his Companions, is performing each prayer at its designated time, according to his statement in the Hadith of Jibreel: "The time is what is between these two," which indicates the impermissibility of delaying the prayer or performing it before its time, except for those with valid excuses such as travelers and the sick.