For it is necessary for you to be patient, so that, by doing the will of God, you may receive the promise
Other versions
King James Version
For ye have need of patience, that, after ye have done the will of God, ye might receive the promise.English Standard Version
For you have need of endurance, so that when you have done the will of God you may receive what is promised.New International Version
You need to persevere so that when you have done the will of God, you will receive what he has promised.