Narrated Abdullah ibn Umar: The Messenger of Allah ﷺ forbade two kinds of food: to sit at cloth on which wine is drunk, and to eat by a man while lying on his stomach. Abu Dawud said: Jafar did not hear this tradition from al-Zuhri. His tradition is rejected.
Related hadith on this topic
Explanation & Benefits
Maulana Ataullah Sajid
Benefits and Issues:
The mentioned narration is weak in its chain of transmission; however, in authentic ahadith, lying on the stomach is generally prohibited. See: (Jami‘ al-Tirmidhi, Book of Manners, Chapter: What Has Been Reported Regarding the Dislike of Lying on the Stomach, Hadith: 2768, and Sunan Abi Dawud, Book of Manners, Hadith: 5040).
So, when would it be permissible to eat while lying in this manner? Furthermore, Shaykh al-Albani rahimahullah has declared the mentioned narration to be hasan (good) due to other supporting evidences; therefore, despite the narration being weak in its chain, it is actionable based on other supporting evidences.
And Allah knows best.
For further details, see: (Silsilat al-Ahadith al-Sahihah, by al-Albani, no. 2394, and al-Irwa’, no. 1982).
Source: Commentary on Sunan Ibn Mājah by Mawlānā ‘Atā’ullāh Sājid, Page: 3370