John 13:14 KJV

[14]If I then, your Lord and Master, have washed your feet; ye also ought to wash one another's feet.

Christians love to do the signs and wonders, the greater works, raise the dead, but when it comes to being nice or forgiving someone, it seems like that is so difficult. God is talking about not just the glorious acts, but this too. And this is the most valuable. It’s easy to love people who are nice to us, but harder for those people who are difficult to love. When we do this we’re confirming Him. It’s a sign and wonder to love the unloveable. When we are obedient we are confirming the cross and bringing glory to God.