It's funny how some people talk about diaper changing as though it involved swallowing slimy grubs. It really doesn't bother me in the least. I've always found it to be a fun time to bond with my babies, talking to them, tickling them, kissing on their feet (until they learn to walk). It's satisfying to tend to someone else's most basic needs. Babies' helplessness is one of the things that makes them most endearing at times. What could be more of an act of service than taking a small stinky person who can't make themselves clean and offering them a fresh start in a nurturing way? After all, Christ does that for us daily...
Justification: "Justification is the work of God where the righteousness of Jesus is reckoned to the sinner so the sinner is declared by God as being righteous under the Law (Rom. 4:3; 5:1,9; Gal. 2:16; 3:11)." -CARM
"Justification is an instantaneous legal act of God in which he (1) thinks of our sins as forgiven and Christ's righteousness as belonging to us, and (2) declares us to be righteous in his sight." - Wayne Grudem
"It will be counted to us who believe in him who raised from the dead Jesus our Lord, who was delivered up for our trespasses and raised for our justification." -Romans 4:24-25
To quote my dad: "God's deal is that He treated Jesus, who was innocent, as if He were guilty, so that He can offer to treat us, who are guilty, as if we were innocent. It's a pretty good deal, and we ought to take it."