Sahih Muslim Book 6, Hadith 61
What prompted him to do this? He said: He wanted that his Ummah should not be put to (unnecessary) hardship.
The Messenger of Allah (ﷺ) observed the noon and afternoon prayers together in Medina without being in a state of fear or in a state of journey. (Abu Zubair said: I asked Sa'id hardship.)
We set out with the Messenger of Allah (ﷺ) on the Tabuk expedition, and he observed the noon and afternoon prayers together and the sunset and 'Isha' prayers together.