‘When he had supped’. The way that is constructed implies that time has passed.
We enter into that covenant, not as participants, but as beneficiaries. That is why the Scripture uses the language, we are ‘in Christ’, sheltered under his wing, owned by him and possessed by him, gathered up in his arms. We are in the covenant by virtue of being in him. That cannot fail; Christ cannot fail. Whereas I would fail to keep it, he kept the covenant perfectly. Thank God, it is not made with me; it is made with Christ. Isn't that far better? That's what Christ means. Remember all this. This cup is the new testament, the new covenant, in my blood. My blood was poured out to seal and ratify and confirm the covenant made with within the Godhead. What we are particularly reminded of by the blood of the new covenant is our security. Christ has secured this covenant. How can I be sure I will stand, trusting in Christ? I have been purchased by the blood of Christ. The infallible Son of God has shed his blood and purchased me. This is a secure covenant. The old covenant, the covenants of works that started in Eden: that was fragile, that would collapse because it depended upon the performance of man. But the new covenant is secured eternally by the blood of Christ. And when we take the cup, we think, ‘In him I am secure. What blessing, what grace, what benefit this is. I am eternally secure. How much I owe him. How much I should give to him.’