When Jeremiah was very young, the Lord appointed him to be a prophet to the nations. "Don't be afraid," the Lord told him, "I am with you and I am with you to deliver you."
When Jesus reminded his listeners of prophets' practice of aiding foreigners, his listeners were incensed. He escaped from their wrath.
The lectionary choice for a psalm to reply to the Jeremiah reading is the first six verses of Psalm 71.
The psalmist is asking the Lord for refuge, deliverance, rescue.
He is asking for help because he needs help and he can remember who has been his help in the past.
A modern discussion centers on why does God allow evil to exist. The question does not arise for this psalmist. Evil does exist, people can be unjust and cruel. And God is the one who can protect him from the wicked.