Rules Don't Work
Nobody can do it. No one can keep the rules. If there is any lesson in the Old Testament, it is that. The history of the Old Testament is the history of failure. In no period of the history of Israel was Israel what God intended it to be. So the Old Testament leads to one conclusion: rules don't work. Paul said it this way.
21 "I do not nullify the grace of God; for if righteousness comes through the Law, then Christ died needlessly"—(Gal 2:21).
If rules and obedience did work for some or all, then it was pointless for Christ to die on the cross. The cross is a very extreme measure. But in fact Paul is saying all other methods were tried and failed, so God had to create an alternative method that guaranteed success, that is what Jesus did on the cross. His death satisfied the law; his resurrection guaranteed he would protect us, and his life as imparted by the Holy Spirit will change our hearts.