John 13:12-15

So when He had finished washing their feet and had put on His garments and had sat down again, He said to them, Do you understand what I have done to you? You call Me the Teacher (Master) and the Lord, and you are right in doing so, for that is what I am. If I then, your Lord and Teacher (Master), have washed your feet, you ought [it is your duty, you are under obligation, you owe it] to wash one another's feet. For I have given you this as an example, so that you should do [in your turn] what I have done to you.