كتاب الفضائل
9
The Book of Virtues
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].

وعنه قال‏:‏ قال رسول الله صلى الله عليه وسلم ‏:‏ ‏ "‏ليس صلاة أثقل على المنافقين من صلاة الفجر والعشاء ولو يعلمون ما فيهما لأتوهما ولو حبوًا‏"‏ ‏(‏‏(‏متفق عليه‏)‏‏)‏‏.‏
Sunnah.com reference : Book 9, Hadith 83
Arabic/English book reference : Book 9, Hadith 1073