Qatada told of hearing that when Allah's Messenger ﷺ 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.” Abu Dawud transmitted it.