romans 8:29 For whom he did foreknow, he also did predestinate to be conformed to the image of his Son, that he might be the firstborn among many brethren. - Free Bible Online

      29. For--as touching this "calling according to his purpose" (Ro 8:28).
      whom he did foreknow he also did predestinate--foreordain. In what sense are we to take the word "foreknow" here? "Those who He foreknew would repent and believe," say Pelagians of every age and every hue. But this is to thrust into the text what is contrary to the whole spirit, and even letter, of the apostle's teaching (see Ro 9:11; 2Ti 1:9). In Ro 11:2, and Ps 1:6, God's "knowledge" of His people cannot be restricted to a mere foresight of future events, or acquaintance with what is passing here below. Does "whom He did foreknow," then, mean "whom He foreordained?" Scarcely, because both "foreknowledge" and "foreordination" are here mentioned, and the one as the cause of the other. It is difficult indeed for our limited minds to distinguish them as states of the Divine Mind towards men; especially since in Ac 2:23 "the counsel" is put before "the foreknowledge of God," while in 1Pe 1:2 "election" is said to be "according to the foreknowledge of God." But probably God's foreknowledge of His own people means His "peculiar, gracious, complacency in them," while His "predestinating" or "foreordaining" them signifies His fixed purpose, flowing from this, to "save them and call them with an holy calling" (2Ti 1:9).
      to be conformed to the image of his Son--that is, to be His sons after the pattern, model, or image of His Sonship in our nature.
      that he might be the first-born among many brethren--"The First-born," the Son by nature; His "many brethren," sons by adoption: He, in the Humanity of the Only-begotten of the Father, bearing our sins on the accursed tree; they in that of mere men ready to perish by reason of sin, but redeemed by His blood from condemnation and wrath, and transformed into His likeness: He "the First-born from the dead"; they "that sleep in Jesus," to be in due time "brought with Him"; "The First-born," now "crowned with glory and honor"; His "many brethren," "when He shall appear, to be like Him, for they shall see Him as He is."

JFB.