Are Christians allowed to use OT for for the Christian doctrines?

For example, many people bring up David as a role model for Christians. These people say, "Look at David, we need to be as close to David as possible, and we need to follow all of the laws that David followed." Since David was so close to God, we need to follow everything that he followed.

While other Christians say that we do not need to follow David, because the things that David said and did were of the Old Testament. These people say, " The teaching of David do not apply to the Christians." These people bring up that David had more than one wife, and that current Christians need to have only one wife.


Which group of people do I need to listen to?