YV 5.2c

' In that he cast it (avartayat), Vrtra is Vrtra; in that he said, 'Hail! wax great, Indra's foe', therefore [1] Indra became his foe. He sprang into life and came into union with Agni and Soma. He grew on all sides an arrow(shot), he enveloped these worlds. Because he enveloped these worlds, therefore is Vrtra, Vrtra. Indra feared him. He ran up to Prajapati, (saying), 'A foe has sprung up for me.' He dipped his bolt and gave it to him, (saying), 'Slay with it.' He went against (him) with it. Agni and Soma said, 'Hurl it not [2]; we are within.' 'Ye are mine', he replied, 'come to me.' They asked for a share; he gave them at the full moon this offering for Agni and Soma on eleven potsherds. They said, 'We are bitten all round, and cannot come.' Indra produced from himself cold and fever heat; that was the origin of cold and fever heat. Him who knows thus the origin of cold and fever heat [3] neither cold nor fever heat slays. By them he led him on, and as he gaped Agni and Soma went forth from him. Then expiration and inspiration deserted him; skill is expiration, intelligence is inspiration; therefore one who gapes should say, 'Skill and intelligence (remain) in me'; verily he places expiration and inspiration in himself and lives all his days. He, having called off the gods from. Vrtra offered at the full moon the oblation to the Vrtra slayer; they slay him at the full moon [4], but make him swell at the new moon; therefore verses are uttered at the full moon referring to the slaying of Vrtra, at the new moon referring to his increase. Having performed the oblation to the Vrtra slayer, he took his bolt and again went against (him). Sky and earth said, 'Hurl it not; he rests in us two.' They said, 'Let us choose a boon.' 'May I be adorned with the Naksatras', said yonder (sky); I May I be adorned with variegated things', said this (earth). Therefore yonder (sky) is adorned with the Naksatras, this (earth) with variegated things.