Musannaf Ibn Abi Shaybah 3385 — Staying away from Isha and Fajr

Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) once led us in prayer. When he had finished the prayer, he saw that there were few people in the mosque. So he said: "Is so-and-so present?" We said: Yes. This went on until he had named three men. Then he said: "There is no prayer heavier for the hypocrites than the Isha and Fajr prayers. If they knew their reward, they would come to the mosque even if they had to crawl on their knees."