Hyssop was among the smallest of the plants (1 Kings 4:33). Here it signifies our faith, which God does not require to be great (Matt. 17:20). The blood of Christ, the Passover lamb, is applied not by great faith but by a small amount of faith. Even a little faith is sufficient for us to apply the blood of Christ that we may enter into Him as the house and have a full enjoyment of the Passover.