John Lightfoot on John 1:4

[In him was life.] The evangelist proceeds from the creation by the Word, to the redemption of the world by the same Word. He had declared how this Word had given to all creatures their first being, verse 3; "All things were made by him": and he now sheweth how he restored life to man when he lay dead in trespasses and sins. "Adam called his wife's name Hevah, life," [Eve, AV Chavah, margin] Genesis 3:20: the Greek reads Adam called his wife's name, 'Life.' He called her Life who had brought in death; because he had now tasted a better life in the promise of the woman's seed. To which it is very probable our evangelist had some reference in this place.

[And the life was the light of men.] Life through Christ was light arising in the darkness of man's fall and sin; a light by which all believers were to walk. St. John seems in this clause to oppose the life and light exhibited in the gospel, to that life and light which the Jews boasted of in their law. They expected life from the works of the law, and they knew no greater light than that of the law; which therefore they extol with infinite boasts and praises which they give it. Take one instance for all: "God said, Let there be light. R. Simeon saith, Light is written there five times, according to the five parts of the law [i.e. the Pentateuch], and God said, Let there be light; according to the book of Genesis, wherein God, busying himself, made the world. And there was light; according to the book of Exodus, wherein the Israelites came out of darkness into light. And God saw the light that it was good; according to the Book of Leviticus, which is filled with rites and ceremonies. And God divided betwixt the light and the darkness; according to the Book of Numbers, which divided betwixt those that went out of Egypt, and those that entered into the land. And God called the light, day; according to the Book of Deuteronomy, which is replenished with manifold traditions." A gloss this is upon light, full of darkness indeed!