Lord’s day 5:
Q12: Since, then, by the righteous judgment of God, we deserve temporal and eternal punishment, how may we escape this punishment and be again received into favor?
A12: God wills that His justice be satisfied; therefore, we must make full satisfaction to that justice, either by ourselves or by another.
2. Rom 8:3-4
Q13: Can we ourselves make this satisfaction?
A13: Certainly not; on the contrary, we daily increase our guilt.
Q14: Can any mere creature make satisfaction for us?
A14: None; for first, God will not punish any other creature for the sin which man committed; and further, no mere creature can sustain the burden of God's eternal wrath against sin  and redeem others from it.
1. Heb 2:14-18
2. Psa 130:3
Q15: What kind of mediator and redeemer, then, must we seek?
A15: One who is a true  and righteous man, and yet more powerful than all creatures, that is, one who is also true God.
DF questions (as you answer these, refer back to Q12-15 for hints):
A) Read Exodus 20:2-6, 23:7, How do we know that God must make satisfaction for our sins?
B) Read Job 15:14-16, How do we know that we can never make satisfaction for our sins? (refer back to A.13)
C) Read Hebrews 2:14-18, Why would an animal or angel not be able to make satisfaction for your sin?
D) Psalm 130:3, Why would another human not be able to make satisfaction for your sin?
E) Read Isaiah 53:9-12, Hebrews 7:26-27, Why was Jesus able to make satisfaction for our sins?