A practical instruction before the words
Dust off the bedding first, then say it.
إِذَا أَوَى أَحَدُكُمْ إِلَى فِرَاشِهِ فَلْيَنْفُضْ فِرَاشَهُ بِدَاخِلَةِ إِزَارِهِ، فَإِنَّهُ لاَ يَدْرِي مَا خَلَفَهُ عَلَيْهِ، ثُمَّ يَقُولُ بِاسْمِكَ رَبِّ وَضَعْتُ جَنْبِي، وَبِكَ أَرْفَعُهُ، إِنْ أَمْسَكْتَ نَفْسِي فَارْحَمْهَا، وَإِنْ أَرْسَلْتَهَا فَاحْفَظْهَا بِمَا تَحْفَظُ بِهِ عِبَادَكَ الصَّالِحِينَ
Bismika rabbī waḍaʿtu janbī wa bika arfaʿuh. In amsakta nafsī fa-rḥamhā, wa in arsaltahā fa-ḥfaẓhā bimā taḥfaẓu bihi ʿibādaka-ṣ-ṣāliḥīn.
“In Your name, my Lord, I lay down my side and by You I raise it. If You take my soul, have mercy on it; and if You release it, protect it with what You protect Your righteous servants.”
The full narration
Narrated Abu Huraira:The Prophet (ﷺ) said, "When anyone of you go to bed, he should shake out his bed with the inside of his waist sheet, for he does not know what has come on to it after him, and then he should say: 'Bismika Rabbi Wada`tu Janbi wa bika arfa'uhu, In amsakta nafsi farhamha wa in arsaltaha fahfazha bima tahfazu bihi ibadakas-salihin
Source
Ṣaḥīḥ al-Bukhārī · 6320
- Agreed upon as authentic (al-Bukhārī / Muslim)