After praying the two rakahs of Fajr, he lay down until he began to breathe deeply. We used to say to Amr that the Messenger of Allah ﷺ said, "My eyes sleep but my heart does not sleep."
حدثنا سفيان عن عمرو قال أخبرني كريب
لما صلى ركعتي الفجر اضطجع حتى نفخ فكنا نقول لعمرو إن رسول الله ﷺ قال تنام عيناي ولا ينام قلبي
Its isnad is sahih. Amr is Ibn Dinar. This hadith is an abridgment of the report about Ibn Abbas praying with the Messenger of Allah ﷺ during his night prayer in the house of Maymuna, which will come again at length several times, including at 3490 and 3502.As for Ibn Uyayna's statement to Amr bin Dinar that the Messenger of Allah ﷺ said, "My eyes sleep but my heart does not sleep," it is mentioned here without its chain of transmission (muallaq), and it will come with a full chain in the Musnad of Abu Hurairah at 7411 and 9655. Its meaning will also come again within another longer hadith of Ibn Abbas at 2514.