But since the intruder was in the guise of Gautama himself, she yielded to his wishes. As Gautama, the sage, returned to his house, he found Indra there, therefore, in great rage, he cursed both Indra and his wife. Indra lost his manhood and had one thousand disgraceful marks on his body. Ahalya became a stone and was to be liberated, when Rama the incarnation of Vishnu would touch her. The moon, who was acting as a watchman of Indra, still has the blemish on his face caused by the impression of the wet towel of Gautama.Gautama was a great ascetic of his age. See : Ahalya and Indra .
References :
1. Kohli, Surindar Singh (ed), Dictionary of Mythological References in Guru Granth Sahib, 1993