JMNT(i)
12 After He had washed their feet, He took His outer garments (= He put them back on) and reclined back again, [and] says to them, "Are you men coming to know and personally understand what I have done for you (to you; in you; with and among you folks)?
13 "You men are repeatedly addressing (calling) Me 'Teacher (= Rabbi)' and 'Lord (Master),' and you keep on speaking (or: saying [it]) beautifully (ideally; finely), for I am.
14 "If I Myself, then, the Lord and the Teacher, wash your feet, you men also are constantly indebted (obliged; continuously owe it) to be habitually washing one another's feet,
15 "for I give (or: gave) an underlying example (or: result of something pointed out as a specimen or illustration shown under your eyes) to you folks, so that just (accordingly; correspondingly) as I Myself do (or: did) for (to; in; among) you, you men should also be repeatedly doing.
16 "Most assuredly (It is certainly true; Amen, amen), I am saying to you, a slave is not greater than his lord (owner; master), nor [is] one sent with a mission (an emissary; a representative) greater than the one sending him.
17 "Since (or: If) you have seen and know these things, you are happy (blessed; fortunate) ones – if you may (or: would; should) be habitually doing them.