I haven’t kept up with this stuff, and I’m sure everyone is way ahead of me here. There’s a lot of great work being done on the Trinity right now and particularly the ramifications of a thorough going Trinitarian take on covenant theology.
But… I thought this was cool: Luke 22 has the last supper and the Passover and of course the institution of the Eucharist. It’s weird that immediately after the Lord’s Supper and the questioning as to who will betray their Lord, the disciples begin disputing about who should be considered the greatest. We know that the disciples were block heads sometimes, and so we (I) tend to read that everywhere. But Jesus doesn’t miss a beat. He connects the dispute to the Lord’s supper in verse 29-30. In 29 Jesus says “And I bestow upon you a kingdom, just as My Father bestowed upon Me.” At least that’s how it reads in my NKJV. But the word for “bestow” is the verb form of diathiki, the word for covenant or testament. Jesus is covenanting with his disciples a kingdom. There’s some stuff there to unpack. But He uses the same word to describe what His Father did: “just as My Father covenanted (it might read) upon Me.” Although I’m not one for ‘proof texts’ per se, this is a fine place to come to prove that a covenant does (or did) exist between persons of the Trinity.
That’s probably old news for you. I think it’s swell. But the other thing is the Kingdom-Covenant connection. The verb form for covenant has this regal connotation going on. To be in covenant is to be a subject of the King. The disciples were a lot quicker than I. They saw the cup of wine, and they heard Jesus tell them that it was His blood. When the ‘testator’ dies, the testament goes into effect (so saith Hebrews 9). The disciples saw the blood, heard the words and immediately they wanted to be made governors and princes. And Jesus didn’t say, “No, there’s no such thing…” He said this is how you get the highest position: by serving.