For he hath strengthened the bars of thy gates - He has made thee safe and secure - as if he had given additional strength to the fastenings of the gates of the city. Cities were surrounded by walls. They were entered through gates. Those gates were fastened by bars passed across them, to which the gates were secured. The language here might be applicable to any period, but it is probable that there is particular reference to Jerusalem as made strong in rebuilding it after the return from Babylon.
He hath blessed thy children within thee - The inhabitants, by giving them safety and peace.