For other useful animals, such as the ass, there was redemption. The ass might be redeemed by a lamb, but if it was not redeemed, its neck was to be broken, Exod. xxxiv. 20. ‘But the firstling of an ass thou shalt redeem with a lamb: and if thou redeem him not, then thou shalt break his neck.’ If redeemed, it was saved from death by substitution. It was redeemed by vicarious death. The lamb was the substitute for the colt, so the lamb died, and the colt was free. You see how the principle of substitution pervades the prophecies of the Jewish ritual. The same principle of substitution appears in the redemption of the first-born sons. But there is a marked difference between that made for them, and that for the animals, viz., that the law did not admit the idea of any such thing as human sacrifice, and therefore the sons were not like the animals subject to death. They belonged to God for service, not for death, and the redemption price was of the same character as the yoke from which they were redeemed. Thus you find the whole tribe of Levi given up as the redemption price of the first-born of the other tribes. The transaction is explained, Num. iii. 41. ‘Thou shalt take the Levites for me (I am the Lord) instead of all the first-born among the children of Israel.’ Thus all the men amongst the Levites were numbered, and all the first-born amongst the other tribes, and by divine authority the Levites were solemnly given up as a substitute for the others, Num. iii 45: ‘Take the Levites instead of all the first-born among the children of Israel, and the cattle of the Levites instead of their cattle: and the Levites shall be mine: I am the Lord.’ But here a difficulty arose, and it is one which teaches us the extreme danger of giving a typical authority to all the institutions of the Old Testament. There was clearly in this case the principle of substitution. The Levites were substituted for the first-born, and the first-born were free. The transaction was, therefore, an illustration of the work of the atonement. But yet if we were to regard it as a divine type of it we should be landed in a most dangerous and unscriptural conclusion, for in the case of the first-born the substituted gift was insufficient; so that if we were to call those Levites a type of the Lord Jesus, we might gather that His sacrifice was insufficient, and required something else as a supplement. Be very careful, therefore, how you call anything a type which is not declared to be one by God Himself.