At Jesus' final Passover service (Matthew 26:27-29), He poured wine into His cup, blessed it, and passed it around to His disciples. Each disciple took a sip from it. Though nowadays we pour wine into many separate vials for Passover, the principle is the same since the wine comes from one source, all of it is blessed together and all of it pictures the same thing—drinking from the cup of the Lamb. Perhaps the meaning is more poignant and easier to grasp by recalling Jesus' Passover service, when the disciples literally took a sip from His cup. When we commemorate this in our Passover service, we are also drinking from the cup of Christ, blessed by our Savior.
Have we consciously rejected the cup of this world, of Babylon, in favor of the "cup of the Lord"? God will not mix the contents of these two cups; they are totally incompatible. We must choose one or the other. Paul says, "We cannot drink of the Lord's cup and of the cup of demons" (I Corinthians 10:21). We must totally reject this world, this Babylon, and that awful cup of the Woman, full of her abominations and of the blood of the saints (Revelation 18:6).
If we have lived in this world—and we all have to some degree—we have sipped from that awful cup and have been affected by its contents. We must now unconditionally reject it, empty it, discard it, and replace it totally in favor of the new cup of blessing from God.
Notice, Christ commands us to drink of His cup! "Drink from it, all of you," Jesus says (Matthew 26:27). He does not say "drink the wine," but to drink of the cup. We know the red wine symbolizes the blood of Christ, shed for the remission of sins (verse 28). We know we need to remember that it took the blood of the Son of God to forgive our sins, and we certainly rehearse that aspect of this service every year. We know that by drinking the wine, we accept His shed blood in our behalf, forgiving our sins and wiping our sinful slate clean. Thank God for that! But drinking of His cup adds so much to the meaning of the Passover wine.
In I Corinthians 10:16, Paul refers to this cup as "the cup of blessing." He asks, "Is it not the communion [margin, fellowship, sharing] of the blood of Christ?" In the Jew's Passover meal, several cups are consumed. Notice what Vine's Expository Dictionary says under article "Cup":
The cup of blessing, I Corinthians 10:16, is so named from the third (the fourth according to Edersheim) cup in the Jewish Passover Feast, over which thanks and praise were given to God.
So as we drink of the cup of the Master, we should understand that it is a wonderful "cup of blessing," thanksgiving, and praise that we offer to God as we drink it!