Musannaf Ibn Abi Shayba 27:126

Waki’ narrated to us, from Hisham ibn ‘Urwah, from his father, who said: Gabriel was delayed in coming to the Prophet, may Allah bless him and grant him peace, so he became extremely distressed. Khadijah said to him, "I see that your Lord has abandoned you, because of what we see of your distress." He said: Then [the verses] were revealed: "By the morning brightness, and by the night when it covers with darkness, your Lord has not taken leave of you, nor has He detested [you]."