One of God’s cardinal natures is Love; for God is Love (1 John 4:8) and yet, other cardinal natures of God includes truth, Justice, Righteousness etc.
“…Righteousness and justice are the foundation of his throne.” Psalm 97:2 (ASV)
This simply means that, though God is Love, yet, He expresses His love in accordance with the Laws of Justice, truth and Righteousness. God’s Love, desires, and eternal purposes are accomplished on legal grounds.
That’s why I say “GRACE is God’s Love, and salvation plan expressed and delivered to men in accordance with the laws of truth, Justice and equity. It is God’s love expressed on legal grounds.
This is because, whatever God does must agree with the laws of justice and equity. That is why God couldn’t let sin go unpunished, though He is Love, kind and merciful.
In order words, as much as God’s love, kindness and mercies might want Him to just let the sinner go unpunished; Equally, His nature of Justice and Righteousness (right judging) would also demand that sin is justly recompensed or paid for.
That’s why under the Old Covenant, the Jews had to offer sin sacrifices, sin offerings and trespass offerings for their sins with animal substitutes year after year.
God’s nature of Love would have made Him desire to just forgive the sins of transgressors freely, yet, His nature of Justice wouldn’t permit that sin goes unpunished. So, by Love, working through Justice and equity; God established a legal way of escaping sin punishment through the law of substitution.
Through the legal law of substitution, transgressors under the Old Testament could escape the death penalty of their transgressions by providing a clean animal without blemish, to offer as a redemptive offering.
“And Aaron shall lay both his hands upon the head of the live goat, and confess over him all the iniquities of the children of Israel, and all their transgressions in all their sins, putting them upon the head of the goat…” Lev 16:21
Through a legal process established by Law, the priest confesses on the qualified animal the sins of the person or people it represents, and it’s killed as a ransom for the life(lives) of the person or people;
“And Aaron shall bring the bullock of the sin offering, which is for himself, and shall make an atonement for himself, and for his house, and shall kill the bullock of the sin offering which is for himself” Lev 16:11
Death is what is written on the price tag of sin; so by the animal dying, the yearly price of sin is paid for and hence, the life of the transgressor is redeemed and preserved.