18 "I do not speak concerning all of you. I know whom I have chosen; but that the Scripture may be fulfilled, 'He who eats bread with Me has lifted up his heel against Me.'
19 Now I tell you before it comes, that when it does come to pass, you may believe that I am He.
20 Most assuredly, I say to you, he who receives whomever I send receives Me; and he who receives Me receives Him who sent Me."
Verse 18 takes up where verse 10 left off.
Christ knew when He chose Judas that he would betray Him. So why choose Him? That Scripture would be fulfilled (Psalm 41:9). Jesus told them in advance so they would understand after it happened. (Acts 1:16)
Lifted up his heel (v. 18) = "given me a great fall," or, "taken cruel advantage." A Hebrew metaphor derived from a horse preparing to kick. See also Genesis 3:15.
the quote (v. 18) is from Psalm 41:9, referring to 2 Samuel 16:20 – 17:3, 23). What David suffered from Ahithophel foreshadowed what David's descendent, Jesus Christ, would suffer from Judas.
The fulfillment of His prediction based on the prophecy of the forty-first Psalm would prove to them His Deity, that He is the omniscient I AM. Psalm 41 refers to the treachery of Ahithopel towards David, and is therefore a prophetic type of Judas's treachery against David's Son and David's Lord. The words which follow verse 20 were spoken by Him to comfort His true disciples and to show them that they were unaffected by Judas's coming betrayal and horrible fall. — The Gospel of John, by Arno Clemens Gaebelein, page 254.
receives Him who sent Me (v. 20) — Jesus assured the other 11 disciples that they were secure (Matthew 10:42).