وَالقَمَرَ قَدَّرناهُ مَنازِلَ حَتّىٰ عادَ كَالعُرجونِ القَديمِ

As for the moon, We have ordained its phases, until it becomes like an old palm leaf.

EXEGESIS

Manāzil (phases) is plural of manzil. It is a place of alighting or descending, stopping, sojourning, lodging, or settling. It also means an abode, a dwelling, and a place where travellers alight on the way. In the context of the verse, it signifies the twenty-eight phases a moon passes through periodically in around twenty-eight days.^{‎[1]Mizan, 17/90.}

ʿUrjūn (palm leaf) is from the quadrilateral root ʿ-r-j-n and occurs only once in the Quran. It means the stem of a palm branch from the point where it emerges off the trunk to the point where the leaves branch off. Because of the weight of the leaves, this part of the branch is usually curved, and as it becomes older, its curvature will increase. Since this part of the wood is yellow, it is like an arched crescent; thus, in this verse, the crescent is likened to an ʿurjūn, which is a few years old.^{‎[2]Mizan, 17/90.}

EXPOSITION

The phases (manāzil) of the moon have apparent effects on the land, sea, and the lives of humans. The twenty-eight places are where the moon passes before its absence on the last two nights of the lunar month. When the lunar month is thirty days, the moon is visible until the twenty-eighth night, in which the moon appears very narrow with a dim-lit yellowish colour which looks like an ʿurjūn. On the two remaining nights the moon will not be visible, which is the phase of the new moon. The simile works beautifully from different aspects. The old moon is likened to the old stem, curved, withered, with its tips drooping down in the dark sky as the ʿurjūn is in the mass of green branches of the palm. 

This remarkable system is a natural celestial calendar that everyone can study. It is through these phases that the passing of the months was originally deduced by man, just as night and day are known from the sun. This fact is alluded to in many other verses of the Quran. They question you concerning the new moons. Say: ‘They are timekeeping signs for the people and [for the sake of] hajj’ (2:189). And more clearly, It is He who made the sun a radiance and the moon a light, and ordained its phases that you might know the number of years and the calculation [of time] (10:5).^{‎[3]Mizan, 17/90.}

INSIGHTS FROM HADITH

1. Imam al-Ṣādiq (a) said to Mufaḍḍal ibn ʿUmar: ‘Use the moon as an obvious indicating sign, for the laymen use it to calculate the months. However, the year’s calculation is not established by it because its motion does not encompass the four seasons nor the times of the blossoming and the ripening of the crops. That is why lunar months and years are left behind solar months and years. Hence, the lunar month moves over [the seasons], so there are times it would correspond to the winter and other times the summer. Consider why the moon shines at night and the ingenuity underlying it. The living beings need the coolness of darkness to get rest and comfort. The complete absence of light and pitch darkness would not have any merit, and do not allow any work possible. Humans may need to undertake some work for want of leisure during the day. Due to extremes of heat, he may work in the moon’s glimmer, for example in agriculture, milking, woodcutting, etc. The moonlight helps humans work for their livelihood whenever they need to do so … In the different phases of the moon, its appearance as a crescent, its disappearance during the nights, in the end its waxing, waning, and its eclipses, there are particular indications that all these changes are all a cause of awareness about the might of God, the exalted, who created it and ordained it for the benefit of the universe, which can serve as instruction for any learner willing to learn from it.’^{‎[4]Mufaḍḍal ibn ʿUmar, Tawḥīd Mufaḍḍal, (Najaf: Ḥaydariyyah Printing, 1955), pp. 81-82.}

INSIGHTS FROM OTHER TRADITIONS

1. He made the moon to mark the seasons, and the sun knows when to go down. You bring darkness; it becomes night, and all the beasts of the forest prowl.^{‎[5]Psalms 104:19-20.}

[1] Mizan, 17/90.
[2] Mizan, 17/90.
[3] Mizan, 17/90.
[4] Mufaḍḍal ibn ʿUmar, Tawḥīd Mufaḍḍal, (Najaf: Ḥaydariyyah Printing, 1955), pp. 81-82.
[5] Psalms 104:19-20.