Inseparably connected with the worship of Indra and Agni is that of the ‘moon-plant,’ soma, the intoxicating personified drink to whose deification must be assigned a date earlier than that of the Vedas themselves.  For the soma of the Hindus is etymologically identified with the haoma of the Persians (the [Greek:  omomi] of Plutarch[12]), and the cultus at least was begun before the separation of the two nations, since in each the plant is regarded as a god.  The inspiring effect of intoxication seemed to be due to the inherent divinity of the plant that produced it; the plant was, therefore, regarded as divine, and the preparation of the draught was looked upon as a sacred ceremony[13].

This offering of the juice of the soma-plant in India was performed thrice daily.  It is said in the Rig Veda that soma grows upon the mountain M[=u]javat, that its or his father is Parjanya, the rain-god, and that the waters are his sisters[14].  From this mountain, or from the sky, accounts differ, soma was brought by a hawk[15].  He is himself represented in other places as a bird; and as a divinity he shares in the praise given to Indra, “who helped Indra to slay Vritra,” the demon that keeps back the rain.  Indra, intoxicated by soma, does his great deeds, and indeed all the gods depend on soma for immortality.  Divine, a weapon-bearing god, he often simply takes the place of Indra and other gods in Vedic eulogy.  It is the god Soma himself who slays Vritra, Soma who overthrows cities, Soma who begets the gods, creates the sun, upholds the sky, prolongs life, sees all things, and is the one best friend of god and man, the divine drop (indu), the friend of Indra[16].

As a god he is associated not only with Indra, but also with Agni, Rudra, and P[=u]shan.  A few passages in the later portion of the Rig Veda show that soma already was identified with the moon before the end of this period.  After this the lunar yellow god regularly was regarded as the visible and divine Soma of heaven, represented on earth by the plant[17].

From the fact that Soma is the moon in later literature, and undoubtedly is recognized as such in a small number of the latest passages of the Rig Veda, the not unnatural inference has been drawn by some Vedic scholars that Soma, in hymns still earlier, means the moon; wherever, in fact, epithets hitherto supposed to refer to the plant may be looked upon as not incompatible with a description of the moon, there these epithets are to be referred directly to Soma as the moon-god, not to soma, the mere plant.  Thus, with Rig Veda, X. 85 (a late hymn, which speaks of Soma as the moon “in the lap of the stars,” and as “the days’ banner”) is to be compared VI. 39. 3, where it is said that the drop (soma) lights up the dark nights, and is the day’s banner.  Although this expression, at first view, would seem to refer to the moon alone, yet it may possibly be regarded as on a par with the extravagant praise given elsewhere to the soma-plant, and not be so significant of the moon as it appears to be.  Thus, in another passage of the same book, the soma, in similar language, is said to “lay light in the sun,” a phrase scarcely compatible with the moon’s sphere of activity[18].