Actually, the concept of the trinity is given in the New Testament, starting in the gospel of John. They wouldn't have used the word 'trinity' of course, since it is an English word, and it is quite possible they didn't have much of an understanding of the deeper concepts about God at that point. But they did recognize Jesus as God manifest in the flesh.
Todays Messianic Jews are just Trinitarians in Hebrew sheeps clothing.
They are Christians who continue to observe the feasts/festivals/holidays of Judaism with an understanding and appreciation of how they point to Jesus, their Messiah.
Assuming for arguments sake that I found NT writings to be inspired the concept of "trinity" still must be interpreted from them.
They are Christians who continue to observe the feasts/festivals/holidays of Judaism with an understanding and appreciation of how they point to Jesus, their Messiah.
Exactly. They are Christians and nothing else.