Dua 4
بِاسْمِكَ رَبِّيْ وَضَعْتُ جَنْبِيْ وَبِكَ اَرْفَعُهٗ فَاِنْ اَمْسَكْتَ نَفْسِيْ فَارْحَمْهَا وَاِنْ اَرْسَلْتَهَا فَاحْفَظْهَا بِمَا تَحْفَظُ بِهٖ عِبَادَكَ الصَّالِحِيْنَ
O my Lord! With Your name I have laid down my side (on the bed), and with Your name I shall raise it. So if You take my soul, have mercy on it, and if You release it, protect it as You protect Your righteous servants.
Sahih al-Bukhari, no. (6320), the wording is his, Sahih Muslim, no. (2741), Sunan Abi Dawud (5050), Sunan at-Tirmidhi, no. (3401), Sunan Ibn Majah, no. (3874)
This hadith teaches that before saying these words a person should dust off the bed three times, then say these words. Dusting it three times is mentioned in Sunan at-Tirmidhi, no. (3401).