"house of israel" refers to the descendants of jacob, the twelve tribes that formed the nation of israel. historically, israel was chosen by god to be a light to the nations, and jesus' ministry began with them to fulfill the promises made to the patriarchs. so he did it to fulfill prophecy and a promise.  > romans 15:8 > for i tell you that christ has become a servant of the circumcised on behalf of gods truth, to confirm the promises made to the patriarchs, > acts 3:25-26 > and you are sons of the prophets and of the covenant god made with your fathers when he said to abraham, through your offspring all the families of the earth will be blessed. / when god raised up his servant, he sent him first to you to bless you by turning each of you from your wicked ways. > isaiah 49:6 > he says: it is not enough for you to be my servant, to raise up the tribes of jacob, and to restore the protected ones of israel. i will also make you a light for the nations, to bring my salvation to the ends of the earth. once jesus fulfilled this he went after the lost sheep of the gentiles (pagans).  > john 10:16 > i have other sheep that are not of this fold. i must bring them in as well, and they will listen to my voice. then there will be one flock and one shepherd. > romans 1:16 > i am not ashamed of the gospel, because it is the power of god for salvation to everyone who believes, first to the jew, then to the greek. > isaiah 56:8 > thus declares the lord god, who gathers the dispersed of israel: i will gather to them still others besides those already gathered. to them still others besides those already gathered.
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