In chronological order, Jesus gave similar teaching four times to His disciples on three occasions:
Sermon on the Mount
(1) “The disciple is not above his master: but every one that is perfect shall be as his master” (Luke 6:40).
Instruction to the Twelve Apostles
(2) “The disciple is not above his master, nor the servant above his lord. 25 It is enough for the disciple that he be as his master, and the servant as his lord. If they have called the master of the house Beelzebub, how much more shall they call them of his household? 26 ¶ Fear them not therefore: for there is nothing covered, that shall not be revealed; and hid, that shall not be known. 27 What I tell you in darkness, that speak ye in light: and what ye hear in the ear, that preach ye upon the housetops. 28 And fear not them which kill the body, but are not able to kill the soul: but rather fear him which is able to destroy both soul and body in hell” (Matt. 10:24-28).
Upper Room Discourse
(3) “Verily, verily, I say unto you, The servant is not greater than his lord; neither he that is sent greater than he that sent him. 17 If ye know these things, happy are ye if ye do them” (John 13:16-17).
(4) “Remember the word that I said unto you, The servant is not greater than his lord. If they have persecuted me, they will also persecute you; if they have kept my saying, they will keep yours also” (John 15:20).
Because Jesus repeated similar teaching about disciples/servants at least four times, these words surely comprise vital instruction from Jesus to every believer!