(vii) Chinuch, Mitzvah #123:
“(The commandment of the sacrifice that varies up and down: To sacrifice the sacrifice that varies up and down for specific sins — and they are: (i) Impurity of the Temple, meaning to say a man who is impure with a primary source of impurity and enters the Temple inadvertently; (ii) likewise, the impurity of its consecrated [foods], that he is impure and ate consecrated meat inadvertently; (iii) an oath of expression, meaning to say that he swore falsely about a thing to do it or not to do it, and the other known angles of an oath of expression, and he transgresses it inadvertently; (iv) likewise an oath of testimony, meaning to say that he swore to his fellow that he does not have testimony for him [when he actually does], whether inadvertently or volitionally.
“For these sins, a person is obligated to bring a sacrifice that varies up and down — meaning to say, according to the wealth or poverty of a person; as it is explicit in the verse (-Leviticus 5:1), ‘And if a soul shall sin and he heard the voice of an oath’ — meaning to say the voice of the oath that they swore him to, whether he knows testimony, ‘if he does not say, he will carry his iniquity.’ And the end of the matter is (-Leviticus 5:6), ‘And he shall bring his guilt-offering.’ And it is not stated there, ‘and it was hidden from him,’ to teach that he is liable for the sacrifice, whether [he is] inadvertent or volitional.)
“...But if he is poor and he brings a ewe or a female goat, he has not fulfilled his obligation. And the reason is that since G-d, blessed be He, had mercy upon him and exempted him with [something less expensive], it is not appropriate that he push himself to bring more than what his hand can reach. And from this, every understanding person will acquire good counsel: to not make expenditures [that are] more than what is fitting according to his money — as this is a cause to steal from the creatures when he seeks that to which he is accustomed and does not find [it].”
