Sunnah.com reference : Book 2, Hadith 306English translation : Book 2, Hadith 397Arabic reference : Book 2, Hadith 402
Narrated [Abu Hurairah (RA)]:
Allah's Messenger (ﷺ) said: "The most burdensome prayers for hypocrites are the 'Isha' and the Fajr prayers and if they knew what (rewards) these (prayers) contain, they would have come to them (in the mosques), even though they had to crawl on their knees."

[Agreed upon].
وَعَنْهُ قَالَ: قَالَ رَسُولُ اَللَّهِ ‏- صلى الله عليه وسلم ‏-{ أَثْقَلُ اَلصَّلَاةِ عَلَى اَلْمُنَافِقِينَ: صَلَاةُ اَلْعِشَاءِ, وَصَلَاةُ اَلْفَجْرِ, وَلَوْ يَعْلَمُونَ مَا فِيهِمَا لَأَتَوْهُمَا وَلَوْ حَبْوًا }  مُتَّفَقٌ عَلَيْه ِ  1‏ .‏‏1 ‏- صحيح.‏ رواه البخاري (657)‏، ومسلم (651)‏.‏