Hadith: When the Prophet (may Allah’s peace and blessings be upon him) went to bed every night, he would join his palms together and blow into them and recite the Surahs al-Ikhlās, al-Falaq, and an-Nās,

عَنْ ‌عَائِشَةَ رضي الله عنها:
أَنَّ النَّبِيَّ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ كَانَ إِذَا أَوَى إِلَى فِرَاشِهِ كُلَّ لَيْلَةٍ جَمَعَ كَفَّيْهِ، ثُمَّ نَفَثَ فِيهِمَا فَقَرَأَ فِيهِمَا: {قُلْ هُوَ اللهُ أَحَدٌ}، وَ{قُلْ أَعُوذُ بِرَبِّ الْفَلَقِ}، وَ{قُلْ أَعُوذُ بِرَبِّ النَّاسِ}، ثُمَّ يَمْسَحُ بِهِمَا مَا اسْتَطَاعَ مِنْ جَسَدِهِ، يَبْدَأُ بِهِمَا عَلَى رَأْسِهِ وَوَجْهِهِ وَمَا أَقْبَلَ مِنْ جَسَدِهِ، يَفْعَلُ ذَلِكَ ثَلَاثَ مَرَّاتٍ.
[صحيح] - [رواه البخاري] - [صحيح البخاري: 5017]

‘Ā’ishah (may Allah be pleased with her) reported:
When the Prophet (may Allah’s peace and blessings be upon him) went to bed every night, he would join his palms together and blow into them and recite the Surahs al-Ikhlās, al-Falaq, and an-Nās, and then he would wipe with his hands over as many parts of his body as he could, starting with his head, face, and the front of his body. He used to do that three times.
Sahih/Authentic. - [Al-Bukhari]

Explanation

It was part of the Prophet's custom that when he went to bed, he would join his palms together and raise them as a supplicant does, and he would blow into them in a mild manner, along with little saliva. Meanwhile, he would recite the three surahs of al-Ikhlās, al-Falaq, and an-Nās. Then, he would wipe with his palms over as much of his body as he could, starting with his head, face, and the front part of his body, repeating this three times.