Man is compared to the donkey in our text and also in Job 11:12, where we are said to be like the wild donkey. We too are unclean before God because we are defiled inwardly and outwardly. We are sinners by nature and by practice.
Although the Israelites were commanded to kill the firstborn donkey by breaking its neck, God provided one way of deliverance. A lamb could be substituted. It was a clean animal and could be used for sacrifice. The lamb could become a substitute for the donkey and die in its place. Only then could the death sentence upon that condemned donkey be lifted and the animal permitted to live.
By this law concerning the redemption of a donkey, God gave a wonderful picture of the gospel. The donkey was freed from the death sentence solely because of the shedding of the blood of the lamb that died in its place. The only means whereby we can escape the sentence of eternal death is by the shedding of the blood of Christ, the Lamb of God. Donkeys were a very common sight in those days and therefore were a constant reminder from God to the people of the need and cost of redemption. Like the Israelites of old we too need to be constantly reminded of the tremendous cost the Saviour paid to redeem us from the condemnation our sins deserved.