Jeremiah
Jeremiah 1:5BSB·traditional attribution

“Before I formed you in the womb I knew you, and before you were born I set you apart and appointed you as a prophet to the nations.”

John Calvin Reformed

Here Jeremiah explains more fully what he had already mentioned that he had been called from above, for otherwise he would have presumptuously obtruded himself: for no one, as the Apostle says, takes this honor to himself; but the call of God alone raises up prophets and teachers to their dignity {see Hebrews 5:4}.

Matthew Henry Presbyterian

Here is, I. Jeremiah's early designation to the work and office of a prophet, which God gives him notice of as a reason for his early application to that business (Jer 1:4, Jer 1:5): The word of the Lord came to him, with a satisfying assurance to himself that it was the word of the Lord and not a delusion; and God told him, 1.

Commenting on Jeremiah 1:4-10

Jamieson-Fausset-Brown Reformed

knew--approved of thee as My chosen instrument (Exo 33:12, Exo 33:17; compare Isa 49:1, Isa 49:5; Rom 8:29). sanctified--rather, "separated." The primary meaning is, "to set apart" from a common to a special use; hence arose the secondary sense, "to sanctify," ceremonially and morally.