Al-Matalib al-'Aliyah 3362 — What to say when lying down to sleep

It is narrated from Sayyidah Aishah (may Allah be pleased with her): "The Messenger of Allah (peace and blessings be upon him) would give instructions about his bedding, and it would be spread out for him; then he (peace and blessings be upon him) would face the qiblah. When he (peace and blessings be upon him) came to his bed to rest, he would make his right palm a pillow, then he would recite something in a low voice, and we did not know what he (peace and blessings be upon him) was saying. Then, when he reached the last part of it, he would raise his voice and supplicate with this du'a: 'Allahumma rabba al-samawati al-sab', wa rabba al-'arshi al-'azim, ilaha wa rabba kulli shay', munzila al-Tawrati wa al-Injili wa al-Furqan, faliqa al-habbi wa al-nawa, a'udhu bika min sharri kulli shay'in anta akhidhun bi-nasiyatih. Allahumma anta al-awwalu fa-laysa qablaka shay', wa anta al-akhiru fa-laysa ba'daka shay', wa anta al-zahiru fa-laysa fawqaka shay', wa anta al-batinu fa-laysa dunaka shay', iqdi 'anna al-dayna wa aghnina min al-faqr' (O Allah, Lord of the seven heavens and Lord of the Mighty Throne, God and Lord of everything, Revealer of the Torah, the Gospel and the Furqan (the Qur'an), Splitter of the grain and the date-stone (so that they sprout), I seek refuge in You from the evil of everything whose forelock is in Your grasp. O Allah, You are the First, so there is nothing before You; You are the Last, so there is nothing after You; You are the Manifest, so there is nothing above You; and You are the Hidden, so there is nothing nearer than You. Settle our debt for us, and free us from poverty and need and make us self-sufficient)."
Imam Abu Ya'la narrated this hadith in his Musnad; al-Sari bin Isma'il in its chain is a weak narrator, but these words of the du'a are narrated in Sahih Muslim from Sayyiduna Abu Hurayrah (may Allah be pleased with him).