The Messenger of Allah ﷺ would not sleep until he had recited Alif Lam Mim, the Sajdah, and "Blessed is He in whose hand is the dominion, and He is over all things competent" [Mulk 67:1].
كان رسول الله ﷺ لا ينام حتى يقرأ الم السجدة، و{تبرك الذي بيده الملك وهو على كل شيء قدير} [سورة الملك: ١].
Tirmidhi (2892), Ahmad (14695), Bukhari in Adab al-Mufrad (1209), and Nasai in Amal al-Yawm wal-Layla (707-708) all narrated it through various routes from Layth bin Abu Salim, from Abu Zubayr, from Jabir, who mentioned it. In its chain is Layth bin Abu Salim, who is daif, but he is corroborated by Mughira bin Muslim al-Khurasani, from Abu Zubayr, and Mughira is truthful (saduq). Bukhari recorded his hadith in Adab al-Mufrad (1207), and Nasai in Amal al-Yawm wal-Layla (706).However, Abu Zubayr did not hear this hadith directly from Jabir. Zuhayr bin Muawiya said, "I asked Abu Zubayr, 'Did you hear Jabir say that the Prophet ﷺ would not sleep until he had recited Alif Lam Meem Tanzil and Tabaraka?'" He said, "Jabir did not narrate it to me, rather Safwan, or Ibn Safwan, narrated it to me." This is recorded by Nasai in Amal al-Yawm wal-Layla (709), and Hakim (2/412).As for Safwan or Ibn Safwan, Mizzi gave his biography in Tahzib Kamal (8/472) and said, "He is Safwan bin Abdullah bin Safwan bin Umaya." I say, he is trustworthy (thiqah) among the men of Tahzib, and it appears that Abu Zubayr narrated it from Safwan, from Jabir, though other views have also been given.Hakim said, "This is a hadith that is sahih according to the criterion of Muslim."As for the statement "he would not sleep until he had recited," it is possible that this refers to the time when one intends to sleep, before the other well-known remembrances. It is also possible that the time is broad, allowing for the recitation of these two surahs at any point before sleeping.