The Book of Mosques and Places of Prayer
حَدَّثَنَا يَحْيَى بْنُ يَحْيَى التَّمِيمِيُّ، قَالَ أَخْبَرَنَا عَبْدُ اللَّهِ بْنُ يَحْيَى بْنِ أَبِي كَثِيرٍ، قَالَ سَمِعْتُ أَبِي يَقُولُ، لاَ يُسْتَطَاعُ الْعِلْمُ بِرَاحَةِ الْجِسْمِ .Abdullah narrated it on the authority of his father Yahya:Knowledge cannot be acquired with sloth
From Sahih Muslim, whose reports the scholars accept as authentic.