They ask thee concerning the New Moons. Say: They are but signs to mark fixed periods of time in (the affairs of) men, and for Pilgrimage. It is no virtue if ye enter your houses from the back: It is virtue if ye fear Allah. Enter houses through the proper doors: And fear Allah: That ye may prosper. Al-Baqarah 2:189 ⧉
Tafsir:
The waxing and waning of the moon are meant to serve only as measures of time. The superstitious believe that the days when the moon is waxing are auspicious while the days of the moon’s waning are inauspicious. The moon, in fact, is an almanac of nature appearing in the sky so that people may plan the timings of their worldly affairs as well as their worship. But there are many people who have come to regard mere outward observance as religiosity.