We have here the gracious provision which the law made for the cleansing of poor lepers. If they were not able to bring three lambs, and three tenth-deals of flour, they must bring one lamb, and one tenth-deal of flour, and, instead of the other two lambs, two turtle-doves or two young pigeons, Lev 14:21, Lev 14:22. Here see, 1. That the poverty of the person concerned would not excuse him if he brought no offering at all. Let none think that because they are poor God requires no service from them, since he has considered them, and demands that which it is in the power of the poorest to give. "My son, give me thy heart, and with that the calves of thy lips shall be accepted instead of the calves of the stall." 2. That God expected from those who were poor only according to their ability; his commandments are not grievous, nor does he make us to serve with an offering. The poor are as welcome to God's altar as the rich; and, if there be first a willing mind and an honest heart, two pigeons, when they are the utmost a man is able to get, are as acceptable to God as two lambs; for he requires according to what a man has and not according to what he has not. But it is observable that though a meaner sacrifice was accepted from the poor, yet the very same ceremony was used for them as was for the rich; for their souls are as precious and Christ and his gospel are the same to both. Let not us therefore have the faith of our Lord Jesus Christ with respect of persons, Jam 2:1.

And if he be poor - he shall take one lamb - There could be no cleansing without a sacrifice. On this ground the apostle has properly observed that all things under the law are purged with blood; and that without shedding of blood there is no remission. Even if the person be poor, he must provide one lamb; this could not be dispensed with: - so every soul to whom the word of Divine revelation comes, must bring that Lamb of God which takes away the sin of the world. There is no redemption but in his blood.

And the priest shall pour of the oil into the palm of his own left hand. See Gill on Lev 14:15.
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Leviticus 14:27

lev 14:27
lev 14:27
lev 14:27And the priest shall sprinkle with his right finger some of the oil,.... See Gill on Lev 14:16.

if he be poor, and cannot get so much; then he shall take one lamb--a kind and considerate provision for an extension of the privilege to lepers of the poorer class. The blood of their smaller offering was to be applied in the same process of purification and they were as publicly and completely cleansed as those who brought a costlier offering (Act 10:34).