The dua for sleeping and for waking

On going to sleep

باسمك اللهم أموت وأحيا

Bismika Allahumma amutu wa ahya.

"O Allah, in Your name I die and I live."

Sahih al-Bukhari 6324.

And another wording, recited with the right hand under the cheek:

اللهم قني عذابك يوم تبعث عبادك

"O Allah, protect me from Your punishment on the Day You raise Your servants."

Sunan Abi Dawud 5045; Jami at-Tirmidhi 3398. Graded sound by the scholars.

On waking

الحمد لله الذي أحيانا بعد ما أماتنا وإليه النشور

Alhamdu lillahi-lladhi ahyana ba'da ma amatana wa ilayhi-n-nushur.

"All praise is for Allah, who gave us life after He caused us to die, and to Him is the resurrection."

Sahih al-Bukhari 6312 and 6324.

Something worth pausing on

The central word of both duas is death — "I die" in the one for sleeping, "He caused us to die" in the one for waking.

That is, the Shariah presents sleep as a small death every night, and waking as a small resurrection. And that is the same subject as the Quran's: "Allah takes the souls at the time of their death, and those that did not die, in their sleep" — Quran 39:42.

And what is recited before sleeping

The virtue of Ayat al-Kursi before sleeping is in Sahih al-Bukhari — Sahih al-Bukhari 2311 — which also says a guard will remain over the one who recites it until morning, and no devil will come near.

And reciting Surah al-Ikhlas and the Mu'awwidhatayn into the palms and wiping them over the body is in Sahih al-Bukhari 5017.