Jesus said it was the work of God. When God gives a command and man obeys man is working the works of God. The act of obedience to Gods command is not the work of man. It is the work of God. Personal obedience to the will of the Lord is the Work of God.
Faith is a work.
Jesus said so. If you are saved by faith, you are saved by works. You cannot believe in salvation by faith and disbelieve in salvation by the works of God. You can believe in salvation by faith and reject the doctrine of salvation by the works of men. You can Believe in salvation by faith in the Lord and disbelieve the proposition of salvation by the works of the law of Moses.