God gave circumcision as an external sign in response to Abraham's faith. [Nigel J][1] points out to a very interesting verse highlighting that

> A servant who is born in your house or who is bought with your money
> shall surely be circumcised; thus shall My covenant be in your flesh
> for an everlasting covenant.
> 
> 
> Genesis 17:13 NASB https://bible.com/bible/100/gen.17.13.NASB

But at some point in history, circumcision became more important than the decision to believe and follow God.

> Circumcise yourselves to the Lord And remove the foreskins of your
> heart, Men of Judah and inhabitants of Jerusalem, Or else My wrath
> will go forth like fire And burn with none to quench it, Because of
> the evil of your deeds.”
>
> Jeremiah 4:4 NASB
> https://bible.com/bible/100/jer.4.4.NASB

What matters to God is doing the things for the right motives. That's what leads Paul to be consistent in his speech, who also does so in Romans 2:29 while quoting from Jeremiah 4:4 when speaking of **circumcision of the heart**, giving emphasis to genuine loyalty to God. That's what God's good, pleasant and perfect will is. If by now you're still considering if God cares about our heart, then why circumcision... go ahead and read Romans 3 where that's addressed.

> Are you so foolish? Having begun by the Spirit, are you now being
> perfected by the flesh?
> 
> Galatians 3:3 NASB https://bible.com/bible/100/gal.3.3.NASB


  [1]: https://hermeneutics.stackexchange.com/a/51064/27054