1 John 2:29 - 3:6 / John 1:29-34
There is a deep connection between parents and their children.
Among other things, every child bears a physical resemblance to the parents.
That's why there are such sayings as "a chip off the old block" or "like father, like son".
John the Baptist calls Jesus the Lamb of God. The Lamb of God takes away the sins of the world by being sacrificed for sinners.
Jesus sacrificed Himself for us so that freed from sin, we can be re-formed and re-created into His image and likeness.
As the 1st reading puts it, we must purify ourselves and try to be as pure as Christ. That is why sin is so serious and devastating.
Because to sin means that we do not know Christ.
But by our baptism, we have become children of God and we have become one with Christ.
In our prayer, let us renounce our sinfulness and profess our faith and our love for God.