The Messiah would be the "New Covenant".
OT Prophecy NT Fulfillment
Isaiah 42:6c
[6] I the LORD have called thee in righteousness, and will hold thine hand, and will keep thee, and give thee for a covenant of the people, for a light of the Gentiles.
Matthew 26:28
For this is my blood of the new testament, which is shed for many for the remission of sins.
Tanakh – Neviim – Isaiah 42:6c
[42:6] I HaShem have called thee in righteousness, and have taken hold of thy hand, and kept thee, and set thee for a covenant of the people, for a light of the nations.
Hebrew OT – Isaiah 42:6c
[42:6] אֲנִי יְהוָה קְרָאתִיךָ בְצֶדֶק
וְאַחְזֵק בְּיָדֶךָ
וְאֶצָּרְךָ
וְאֶתְּנָךָ לִבְרִית עָם
לְאוֹר גּוֹיִם