John Gill Commentary Jeremiah 15:20

"And I will make thee unto this people a fortified brazen wall; and they shall fight against thee, but they shall not prevail against thee; for I am with thee to save thee and to deliver thee, saith Jehovah." — Jeremiah 15:20 (ASV)

And I will make you unto this people a fenced brasen wall ,
&c.] As he had promised him, when he first called him to his office, (Jeremiah 1:18) , and so would not be as a liar to him: and they shall fight against you ;
by words and blows, by menaces and imprisonment: but they shall not prevail against you ;
so as to cause him to call in his words, and contradict his prophecies; or so as to take away his life: for I am with you, to save you, and deliver you, saith the Lord ;
the presence of God with his ministers is sufficient to save and deliver them out of all their troubles, and to protect and defend them against all their enemies; see (Matthew 28:20) .