'Ubida b. Samit reported that when wahi (inspiration) descended upon Allah's Messenger (ﷺ), he felt a burden on that account and the colour of his face underwent a change.
Sahih Muslim Book 43, Hadith 118
← Previous Hadith How does the the wahi (inspiration) come to you? He said: At times it comes to me like the ringing of a bell and that is most severe for me and when it is over I retain that (what I had received in the form of wahi), and at times an Angel in the form of a human being comes to me (and speaks) and I retain whatever he speaks.

Sahih Muslim Book 43, Hadith 117 Next Hadith → 'Ubida b. Samit reported that when wahi descended upon Allah's Apostle (ﷺ), he lowered his head and so lowered his Companions their heads, and when (this state) was over, he raised his head.

Sahih Muslim Book 43, Hadith 119