Riyad as-Salihin

Abu Hurairah (May Allah be pleased with him) reported: The Messenger of Allah (ﷺ) said, "No Salat is more burdensome to the hypocrites than the Fajr (dawn) prayer and the 'Isha' (night) prayer; and if they knew their merits, they would come to them even if they had to crawl to do so."

[Al-Bukhari and Muslim].