Mishkat al-Masabih, hadith 2345

وَعَن قَتَادَة: بَلَغَهُ أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ كَانَ إِذَا رَأَى الْهِلَالَ قَالَ: «هِلَالُ خَيْرٍ وَرُشْدٍ هِلَالُ خَيْرٍ وَرُشْدٍ هِلَالُ خَيْرٍ وَرُشْدٍ آمَنْتُ بِالَّذِي خَلَقَكَ» ثَلَاثَ مَرَّاتٍ ثُمَّ يَقُولُ: «الْحَمْدُ لِلَّهِ الَّذِي ذَهَبَ بِشَهْرِ كَذَا وَجَاء بِشَهْر كَذَا» . رَوَاهُ أَبُو دَاوُد

Qatada told of hearing that when God’s messenger 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 God who has made such and such a month to pass and has brought such and such a month.” Abu Dawud transmitted it.