Riyad us Saliheen: Hadith 1227

At the sight of the new moon (of the lunar month), the Prophet (ﷺ) used to supplicate: "Allahumma ahillahu 'alaina bil-amni wal-iman, was-salamati wal-Islam, Rabbi wa Rabbuk-Allah, Hilalu rushdin wa khairin (O Allah, let this moon appear on us with security and Iman; with safety and Islam. (O moon!) Your Rubb and mine is Allah. May this moon be bringing guidance and good)."

[At- Tirmidhi].