John Gill Commentary Isaiah 61:9

"And their seed shall be known among the nations, and their offspring among the peoples; all that see them shall acknowledge them, that they are the seed which Jehovah hath blessed." — Isaiah 61:9 (ASV)

And their seed shall be known among the Gentiles, and their
offspring among the people
Not only the Jews will be converted as a body in the latter day, but there will be a succession of converts among them in later ages, and will be known among Christian Gentiles by their faith and love, and good works and holy conversation; and will be taken notice of and acknowledged by them as brethren, and will be famous among them for religion and godliness:

all that see them shall acknowledge them, that they are the seed which
the Lord has blessed ;
that they are the spiritual seed of Abraham, as well as his carnal seed, and are blessed with him; blessed with all spiritual blessings in Christ, with faith in him, and with every other grace.