"When he had finished washing their feet, he put on his clothes and returned to his place. "Do you understand what I have done for you?" he asked them. "You call me 'Teacher' and 'Lord,' and rightly so, for that is what I am. Now that I, your Lord and Teacher, have washed your feet, you also should wash one another's feet. I have set you an example that you should do as I have done for you. I tell you the truth, no servant is greater than his master, nor is a messenger greater than the one who sent him. Now that you know these things, you will be blessed if you do them." ~ John 13
We can argue until the cows are extinct about whether Jesus was talking about literally or figuratively washing each other's feet, and my best guess is that if our answer is only one or the other, we're wrong.
But let's just ignore that little quibble for a moment and go to the last verse in the citation: "... you will be blessed if you do them."
What Paul tells the Ephesians is the "first commandment with a promise" is also one that Jesus cites at least twice in scripture (Matthew 15:4 / Mark 7:10; Matthew 19:19 / Mark 10:19): "Honor your father and mother." The promise? " ... so that you may live long in the land the LORD your God is giving you."
In fact, these are not the only two instructions which are connected with blessing. Paul said "first commandment." Around the table of that last supper, Jesus mentioned, "these things" and "do them," plural. When a woman interrupted His teaching about the war between good and evil to say, "Blessed is the mother who gave you birth and nursed you," He responded, "Blessed rather are those who hear the word of God and obey it" (Luke 11:28).
Do we really believe that?
Do we have a sense for why words expressing "blessing" outnumber words expressing "cursing" in scripture about two to one; "salvation" outpacing "condemnation" about five to one?
Do we understand why the longest chapter in the Bible - Psalm 119 (and almost at the center of it) - is a paean of praise for God's instructions; an expression of delight in meditating on them; a thanksgiving for the blessing of having them?
Because they're not just good, they're good for us.
Do we take Jesus at His word when He says, in effect, "You will be blessed if you just do it!"?