the righteous standard of the law … might be fulfilled in us. The Greek preposition en ("in") can be understood in more than one way. It may mean that the law is fulfilled in us because we are united with Jesus Christ, who fully obeyed the law for us. It can also mean that, by freeing us from the power of sin, Jesus Christ enables us to please God and live out the true purpose of the law.
In the Old Testament, the flesh refers to human weakness and slavery to sin (see Genesis 6:3, 12; Psalm 78:39; Isaiah 40:6; also in Romans 8:5–9, 12–13). Paul uses this phrase to describe the conflict between the human tendency to sin and the Holy Spirit.