C. F. Keil and Franz Delitzsch on Jeremiah 1:8

Jer 1:8

Just as little needs youthful bashfulness or shy unwillingness to speak before high and mighty personages stand as a hindrance in the way of his accepting God’s call. The Lord will be with him, so that he needs have no fear for any man. The suffix in מפניהם refers to all to whom God sends him (Jer 1:7). These, enraged by the threatenings of punishment which he must proclaim to them, will seek to persecute him and put him to death (cf. Jer 1:19); but God promises to rescue him from every distress and danger which the fulfilment of his duties can bring upon him. Yet God does not let the matter cease with this pledge; but, further, He consecrates him to his calling.