Jeremiah 1:5

Before I formed thee in the belly I knew thee
Not merely by his omniscience, so he knows all men before their conception and birth; but with such a knowledge as had special love and affection joined with it; in which sense the Lord knows them that are his, as he does not others, and predestinates them unto eternal life; and which is not only before their formation in the womb, but before the foundation of the world, even from all eternity. The forming of the human foetus is God's act, and a curious piece of workmanship it is; see ( Psalms 139:15 Psalms 139:16 ) . And before thou camest forth out of the womb I sanctified thee;
not by infusing holiness into him, but by separating him in his eternal purposes and decrees to the office of a prophet before he was born, and even before the world began; just as the Apostle Paul was separated to the Gospel of God, ( Romans 1:1 ) , for it follows, and I ordained thee a prophet unto the nations;
not to the Israelites only, who Jarchi thinks are so called, because they now followed the usages and customs of the nations; but to the Gentiles, against whom be was sent to prophesy, ( Jeremiah 46:1 ) as Egyptians, Philistines, Moabites, Ammonites, and Chaldeans. This ordination of him to be a prophet was not done in time, but in eternity, in the mind and thought of God; he was foreordained to this office before the foundation of the world, of which a declaration was made unto him when he was now called unto it; to which he makes answer.