Albert Barnes on John 5:45-46

Do not think that I will accuse you. Do not suppose that I intend to follow your example. They had accused Jesus of breaking the law of God, Jn 5:16. He says that he will not imitate their example, though he implies that he might accuse them.

To the Father. To God.

There is one that accuseth you. Moses might be said to accuse or reprove them. He wrote of the Messiah, clearly foretold his coming, and commanded them to hear him. As they did not do it, it might be said that they had disregarded his command; and as Moses was divinely commissioned and had a right to be obeyed, so his command reproved them: they were disobedient and rebellious.

He wrote of me. He wrote of the Messiah, and I am the Messiah, Gen 3:15, 12:3; comp. Jn 8:56, Gen 49:10, De 18:15

(u) "there is one" Rom 2:12.