“[…] If you had understood what this means, ‘I want mercy and not sacrifice,’ you would not have condemned the guiltless ones.”
~Matthew 12:7

Often we think of mercy as an accessory to justice. But really, justice is a means for God to express his mercy toward us.
Because of his mercy, Jehovah God sent his only-begotten son to earth to die for our sins. (Ro. 5:8-11)
Jesus thereby satisfied God’s law of ‘a life for a life,’ replacing Adam as our first father, and opened the way for us to reconcile with God. (De. 19:21; 1 Cor. 15:45)
God’s law was founded on mercy, so Jesus highlighted mercy as the underlying principle in the application of his law.
If we are motivated by a sincere desire to aid those who are at a spiritual or material disadvantage, our heavenly Father takes notice. (Prov. 19:17; 2 Cor. 4:1,2)