Agni, in the Vedas, is described as the purifier. He is considered the essence of life, the fundamental life-energy. He is equated to will power and strength.
Translation by Sri Aurobindo: "For he is the will, he is the strength, he is the effector of perfection, even as Mitra he becomes the charioteer of the Supreme. To him, the first, in the rick-offerings the people seeking the godhead utter the word, the Aryan people to the fulfiller."
Sa hi rtuhu sa maryaha sa saadhur
mithro na bhoodhadhbuthasya ratheehi!
Tham medheshu prathamam devayantheervisha
upa bruvathe dhasmamaareehi!!
Rig Veda I.77