Why didn't the disciples understand the Lord's Supper at the Last Passover?
At the last Passover, the eleven did not understand because the Lord's Supper memorializes His death, which had not yet happened. Jesus did not explain it then, since it was not yet time; its meaning awaited progressive revelation. Paul later explains in 1 Corinthians 11 that the bread and cup show the Lord's death until He comes.
Les teaches that this is progressive revelation. The 11 at the night of the Passover didn't understand it, and Jesus did not explain it because it wasn't time for it. The Lord's table of bread and cup is a memorial of His death, and at the last Passover His death had not yet happened. Paul writes in 1 Corinthians 11:23-26 what he received from the Lord: the same night Jesus was betrayed He took bread, gave thanks, broke it, and said, “Take, eat; this is my body, which is broken for you; this do in remembrance of me.” After the same manner He took the cup, saying, “This cup is the New Testament in my blood; this do ye, as oft as ye drink it, in remembrance of me.” Verse 26 gives the explanation: as often as you eat this bread and drink this cup, you show the Lord's death until He comes. The purpose of the Lord's Supper is nothing more and nothing less than remembering what Christ accomplished on the cross—His body broken and His blood poured out. Back in Genesis, the picture is His death, burial, and resurrection.