9. But doesn’t God do us an injustice by requiring in his law what we are unable to do?
No. God created humans with the ability to keep the law. They, however, tempted by the devil, in reckless disobedience, robbed themselves and all their descendants of these gifts.
Ge 1.31; Eph 4.24
Ge 3.13; Jn 8.44
10. Will God permit such disobedience and rebellion to go unpunished?
Certainly not. He is terribly angry about the sin we are born with as well as the sins we personally commit. As a just judge he punishes them now and in eternity. He has declared: ‘Cursed is everyone who does not continue to do everything written in the Book of the Law.’
Ex 34.7; Ps 5.4-6; Na 1.2; Ro 1.18; Eph 5.6; Heb 9.27
Dt 27.26; Gal 3.10
11. But isn’t God also merciful?
God is certainly merciful, but he is also just. His justice demands that sin, committed against his supreme majesty, be punished with the supreme penalty–eternal punishment of body and soul.
Ex 34.6-7; Ps 103.8-9
Ex 34.7; Dt 7.9-11; Ps 5.4-6; Heb 10.30-31
From the Heidelberg Catechism.