I work frequently as an elementary school substitute teacher, and it’s often funny to see the kids’ faces when they first walk into the classroom. You can see the first bewilderment, where’s our teacher? And then sometimes, some whispering and excitement because they think they’ll get off with an easy day and no rules!

When we talk about Christ being our substitute, it’s not quite the same idea. As a substitute teacher, I’m not considered (at least by the students) to be as good as the normal teacher. Just an adult to maintain order while the teacher happens to be out.

But our need for a substitute comes from the fact that we don’t just need a guide in life’s journey or someone to finish off our salvation “after we’ve done all we can” (like the Mormons say). Every attempt on our part to meet God’s standard leaves us more indebted to him, because every good deed is tainted by sin. “All of our righteous acts are like filthy rags” (Is. 64:6, ESV). Even if I were to suddenly cease sinning and start doing nothing but good deeds the rest of my life, I would still have the entire debt of my past sins weighing against me!

We’re lost in a hopeless attempt without a substitute, someone who can pay our debt and live the perfect life we are commanded to live in our place. To me, this exchange is one of the most beautiful aspects of the gospel. Christ has taken my filthy garments of sin on himself and endured their punishment, while giving me his perfect garments of righteousness so that God looks at me and only sees a perfect Christ! “For our sake he made him to be sin who knew no sin, so that in him we might become the righteousness of God” (2 Cor. 5:21, ESV).

This means that every day going forward, God looks at me and is pleased because of Christ. “I love to work for God in the daytime and at night to lie down under his smiles,” Sarah Edwards said. How do I know God smiles at me when I lie down, especially when I still sin every day? Because he is looking upon Christ’s perfect life! Regardless of whether I feel good about my Christian walk on a given day or not, “there is no condemnation for those who are in Christ Jesus” (Rom. 8:1).

Take a moment to think through the beautiful implications of this by reading this hymn:

His robes for mine: O wonderful exchange!

Clothed in my sin, Christ suffered ’neath God’s rage.

Draped in His righteousness, I’m justified!

In Christ I live, for in my place He died.

I cling to Christ, and marvel at the cost:

Jesus forsaken, God estranged from God.

Bought by such love, my life is not my own:

My praise—my all—shall be for Christ alone.

His robes for mine, what cause have I for dread?

God’s daunting Law Christ mastered in my stead.

Faultless I stand, with righteous works not mine,

Saved by my Lord’s vicarious death and life!

His robes for mine: God’s justice is appeased.

Jesus is crushed, and thus the Father’s pleased.

Christ drank God’s wrath on sin, then cried “Tis done!”

Sin’s wage is paid; propitiation won!

His robes for mine: such anguish none can know.

Christ, God’s beloved, condemned as though his foe.

He, as though I, accursed and left alone;

I, as though He, embraced and welcomed home!^[5]