Walking according to the Spirit rather than the flesh (see Galatians 5:16-24).
Now what I am commanding you today
is not too difficult for you or beyond your reach. 12 It is not up in heaven, so that you have to ask, “Who will ascend into heaven to get it and proclaim it to us so we may obey it?”
13 Nor is it beyond the sea, so that you have to ask, “Who will cross the sea to get it and proclaim it to us so we may obey it?”
14 No, the word is very near you; it is in your mouth and in your heart so you may obey it.
15 See, I set before you today life and prosperity, death and destruction.
16 For I command you today to love the Lord your God, to walk in obedience to him, and to keep his commands, decrees and laws; then you will live and increase, and the Lord your God will bless you in the land you are entering to possess Deut 30:11-16
He has made us competent as ministers of a new covenant—not of the letter but of the Spirit;
for the letter kills, but the Spirit gives life.
7 Now if the ministry that brought death, which was engraved in letters on stone, came with glory, so that the Israelites could not look steadily at the face of Moses because of its glory, transitory though it was,
8 will not the ministry of the Spirit be even more glorious?
9 If the ministry that brought condemnation was glorious, how much more glorious is the ministry that brings righteousness!
2Cor3:6-9
Moses said it would not be too difficult or beyond the reach of the Israelites to obey the law handed down at Sanai. However, Paul stated the letter killed and was the ministry of death and condemnation. Why the difference between the two?
In my view, Moses was speaking of the Spirit of the law, and Paul the letter of the law. It is impossible for man to perfectly obey the letter of ‘’thou shalt not’’ There is no wiggle room for error. Perfectly obey the law or stand guilty before it. If even one person could have perfectly obeyed the letter there would have been no need for Christ to die at Calvary for peoples sins, for it would have been possible for man never to commit sin. Paul had been an ardent Pharisee, the letter of the law was everything.
I believe Moses was speaking of the Spirit of the law, in respect that the people should in their hearts want to follow the law. But though they would want to follow it and their lives would generally reflect obedience to it, they never would perfectly obey the law/the letter of the law due to human limitations. That should not be so difficult to do, for the limitations of man are allowed for. That in my view is the difference between the letter of the law and the Spirit of the law