For you know that you will receive from the Lord the repayment of an inheritance. Serve Christ the Lord
Other versions
King James Version
Knowing that of the Lord ye shall receive the reward of the inheritance: for ye serve the Lord Christ.English Standard Version
knowing that from the Lord you will receive the inheritance as your reward. You are serving the Lord Christ.New International Version
since you know that you will receive an inheritance from the Lord as a reward. It is the Lord Christ you are serving.