For freedom Christ has set us free. Stand firm, therefore, and do not submit again to a yoke of slavery.
Listen! I, Paul, am telling you that if you let yourselves be circumcised, Christ will be of no benefit to you. Once again I testify to every man who lets himself be circumcised that he is obliged to obey the entire law. You who want to be justified by the law have cut yourselves off from Christ; you have fallen away from grace. For through the Spirit, by faith, we eagerly wait for the hope of righteousness. For in Christ Jesus neither circumcision nor uncircumcision counts for anything; the only thing that counts is faith working through love.
(Lectionary, New Revised Standard Version)
I can remember as a teenager helping my father to untangle his fishing line. We spent many evenings trying to undo the knots and after hours only achieving a few feet of plastic line. It was never-ending, but it left me with a desire to undo knots rather than waste string or wool or twine.
The Apostle Paul has been trying to undo a 'tangle', that is the confusion that Christian-Jews have caused for the new Gentile-Christians in Galatia, about whether or not they should be circumcised and obey the whole of the Law. He now begins to bring his discussion towards a conclusion, arguing that as Christians they have been freed from the restrictions of the old commands of the Law, so why would they want to go back to that kind of slavery? He's not saying there is no law, after all Jesus taught the ultimate commandment, that we should love God, and love our neighbour as ourself (Mark 12.30-31), but by returning to the demands of the old Law they have rejected Christ's loving sacrifice that He made for them. In trying to earn their way back to God, they have rejected hope for their future - of eternal life.
In our world today many think freedom is having everything they desire and doing anything they want. Life has a way of proving otherwise, and this heedless attitude takes little concern of others. Paul argues that real freedom is being free from sin and guilt, and living in hope for all that God offers. Ultimately all that matters is to have faith and to allow that faith to show its existence in our actions - for God, our family, our neighbour, and for the wider world.
Lord Jesus Christ,
we thank You for the freedom
You won for us
by Your sacrifice on the cross.
You ensured that our sins will be forgiven,
when we make a genuine confession,
and that we can be reunited with
our Heavenly Father.
Let us never take this for granted,
but approach the throne of Grace
with humble and penitent hearts.
Then may we go out and put that faith
into action.
Amen.
This Wikihow article that looks at sin (with pictures) is pretty good if you bear in mind it's trying to speak to Christians of all denominations: