। ॥
In plain words
The Veda has no beginning. The one who brings it to light is Īśa, whose very nature is light that needs no other light. The wise looked at that shining forth, and said of it: this is pramāṇa — a valid means of knowing.
Close to the Sanskrit
The Veda is beginningless; its manifester is Īśa, whose nature is self-luminous. Having observed that manifestation of it, this [Veda] was declared by the wise to be pramāṇa — thus.