Jesus also gives a practical application of his action. As their Lord he commanded his disciples to imitate him by washing one another’s feet. He is not teaching a literal imitation, although that would be appropriate in hot countries. Rather he wants each of his disciples to be alert to potential defilement in other believers.
For example, James describes one such scenario in James 5:19-20: ‘My brothers, if anyone among you wanders from the truth and someone brings him back, let him know that whoever brings back a sinner from his wandering will save his soul from death and will cover a multitude of sins.’ Paul describes such activity in Romans 14:19: ‘So then let us pursue what makes for peace and for mutual upbuilding.’ If we see a fellow-Christian doing something that defiles him, it is our Christian responsibility to personally go and point out in a loving manner his situation. Sometimes we may need to involve others, but we cannot absolve our responsibility.
Are there any qualifications needed for foot washing? I would suggest three. First, we can only engage in foot washing after we have been cleansed ourselves (in both senses of cleansing at conversion and daily cleansing). Somebody with dirty hands cannot clean somebody else. Second, watch the temperature of the water as we foot wash the other person. It should not be too hot (with anger) or too cold (without love). Third, we should be willing to let others wash our feet.
Jesus says that engaging in foot washing is a route of spiritual blessing for his disciples: ‘If you know these things, blessed are you if you do them’ (John 13:17).