Ibn al-Sari reported: Abu al-‘Alyiah, may Allah have mercy on him, said, “The fasting person is in an act of worship as long as he does not backbite anyone, even if he is sleeping on his bed.”
Source: al-Zuhd li Hannād ibn al-Sarī 1202
عن هناد بن السري عَنْ أَبِي الْعَالِيَةِ رحمه الله قَالَ الصَّائِمُ فِي عِبَادَةٍ مَا لَمْ يَغْتَبْ وَإِنْ كَانَ نَائِمًا عَلَى فِرَاشِهِ
1202 الزهد لهناد بن السري باب الغيبة للصائم