Isaiah 61 – Why a double portion? To whom is it given? Who is His first-born?

Isa 61:7
Instead of your shame you will have a double portion, And instead of humiliation they will shout for joy over their portion. Therefore they will possess a double portion in their land, Everlasting joy will be theirs.

Elohim will grant his people a double portion.

Deut. 21:17 “But he shall acknowledge the first-born, the son of the unloved, by giving him a double portion of all that he has, for he is the beginning of his strength; to him belongs the right of the first-born.

Because Israel is His first-born.

Ex. 4:22 “Then you shall say to Pharaoh, ‘Thus says the LORD, “Israel is My son, My first-born.