Abu Dawud Book 36, Hadith Number 5073.

Narated By Qatadah : When the Prophet of Allah (PBUH) saw the new moon, he said: “a new moon of good and right guidance; a new moon of good and right guidance; a new moon of good and right guidance. I believe in Him Who created you” three times. He would then say: “Praise be to Allah Who has made such and such a month to pass and has brought such and such a month.”