When the Messenger of Allah (may Allah's peace and blessings be upon him) received revelation, he felt distressed and the color of his face changed
Authentic hadithعن عبادة بن الصامت رضي الله عنه ، قال: «كان نبيُّ اللهِ صلى الله عليه وسلم إذا أُنْزِلَ عليه الوحيُ كُرِبَ لذلك وتَرَبَّدَ وجهُه».
‘Ubādah ibn As-Sāmit (may Allah be pleased with him) reported: When the Messenger of Allah (may Allah's peace and blessings be upon him) received revelation, he felt distressed and the color of his face changed
Explanation
Whenever the Prophet (may Allah's peace and blessings be upon him) received revelation, he would experience hardship and distress to the extent that the color of his face would change due to the gravity and difficulty of that matter. Besides, the Prophet (may Allah's peace and blessings be upon him) paid much attention and care to the revelation and showed great awe to whatever he was asked to observe, such as fulfilling the rights of servitude, showing due gratefulness to Allah, the Almighty, and glorifying His commands and reports.
Source · Narrated by Muslim
From the Hadith Encyclopedia (hadeethenc.com).