These verses start with an urgent call to action.  “Mark my words” means ‘make sure that you understand this’, ‘pay close attention’.  Paul wrote very strongly because his readers’ eternal lives were at risk if they did not keep on trusting Jesus alone for their salvation (1 Corinthians 15:2).  The apostle was warning against Jewish-background teachers who were pressurising male Gentile believers to be circumcised if they wanted to be accepted in God’s family.  The teaching was wrong.  It was an unnecessary and redundant instruction for Christians.  It also denied the grace of God in Christ.

It was a real dilemma for the apostles to resolve.  Until Jesus rose from the dead, and the Holy Spirit was given to all believers, circumcision was a God-given physical sign of belonging to Him (Genesis 17:9-14).  But, in His death and resurrection, Jesus had fulfilled the Old Testament law (Romans 10:4).  You can read the apostles’ discussion and the conclusion they reached (Acts 15:1-11).  Since then, circumcision of the body has been replaced by circumcision of the heart (Romans 2:28-29).  
 
Paul also told the Christians that if they thought they could be saved by keeping the law, they had fallen away from the grace of Christ, which is the only way people can be truly saved (Ephesians 2:8-9).  Everyone who loves God longs to be perfect, but none of us can be declared righteous because of what we do, because nobody can keep His law completely.  And so, Jews who believe in Jesus are not more special than Gentile Christians because nobody is saved by law-keeping.  What matters is admitting you are a sinner and trusting Jesus to be your Saviour (www.crosscheck.org.uk). That sort of faith will welcome the Holy Spirit and allow Him to produce love in our lives, which will be a blessing to everybody (Romans 13:8).
 
Love is the real mark of faith.  It shows kindness to people who do not deserve it; and forgives those who repent.  The love produced by faith in Jesus is full of grace, and marks people out as children of God.  That love comes through faith in Jesus.  Love is the most powerful of all the identifiable characteristics of a human being.  Genuine love cannot be manufactured or done as a ‘good work’; it has to come from inside us … and it gets there because God gives us His Holy Spirit.  Romans 5:5 says, “… God’s love has been poured out into our hearts through the Holy Spirit, who has been given to us.”  The Spirit is not given because we are good, but because God is good, and honours all who are trusting in the death and resurrection of Jesus for their salvation.