The Messiah would come to bring Israel back to God.
OT Prophecy NT Fulfillment
Isaiah 49:5b
"And now, saith the LORD that formed me from the womb to be his servant, to bring Jacob again to him, Though Israel be not gathered, yet shall I be glorious in the eyes of the LORD, and my God shall be my strength."
Matthew 15:24
"But he answered and said, I am not sent but unto the lost sheep of the house of Israel."

Matthew 10:5–7
[5] These twelve Jesus sent forth, and commanded them, saying, Go not into the way of the Gentiles, and into any city of the Samaritans enter ye not:
[6] But go rather to the lost sheep of the house of Israel.
[7] And as ye go, preach, saying, The kingdom of heaven is at hand.
Tanakh – Neviim – Isaiah 49:5b
"And now saith HaShem that formed me from the womb to be His servant, to bring Jacob back to Him, and that Israel be gathered unto Him—for I am honourable in the eyes of HaShem, and my G-d is become my strength—"
Hebrew OT – Isaiah 49:5b
[49:5] וְעַתָּה אָמַר יְהוָה
יֹצְרִי מִבֶּטֶן לְעֶבֶד לוֹ
לְשׁוֹבֵב יַעֲקֹב אֵלָיו
וְיִשְׂרָאֵל לֹא יֵאָסֵף
וָאֶכָּבֵד בְּעֵינֵי יְהוָה
וֵאלֹהַי הָיָה עֻזִּי