en_tn/2pe/02/20.md

Whoever escapes the defilements of the world through the knowledge of the Lord and Savior Jesus Christ,

Any person that has accepted the Lord and Savior Jesus Christ and turned from unclean and unholy living.

it has become for them worse than at the first.

They are worse off because they have knowledge of holy living and have chosen to return to a life of sin.

have known the way of righteousness

Living a life pleasing to God.

holy commandment delivered to them.

God's rules and laws given to them so they would know how to live for God.

This proverb...a dog returns to its own vomit. A washed pig returns to the mud.

A wise saying that is comparing how those that know the truth but returns to ungodly living. "A dog returns to its own vomit" refers to proverbs 26:11. In either case the meaning is "the animal is unable to be trained not to defile itself."