I will bring the blind by a way that they knew not. "The blind" here can only be captive Israel, still dim-sighted from the effect of its old sins against light, and therefore greatly needing God's guidance.
God promises to "bring them" out of captivity "by a way not hitherto known to them"—the way of voluntary release by the favour of a new king (see the comment on Isaiah 42:9). I will make darkness light before them; either, I will illuminate with rays of light and hope the dark and cheerless life that they have been leading (Delitzsch), or, I will throw light upon that dark future which has hitherto stretched before them, and allow them to penetrate its obscurity, and see what is about to happen.
Crooked things; rather, rough places; i.e. difficulties of any and every kind. Straight; rather, smooth, level, flat,. These things will I do unto them, and not forsake them. Dr. Kay translates, "These things have I done, and have not forsaken them;" Mr.
Cheyne, "These are the things that I will do, and will not let them slip;" Delitzsch, "These are the things that I carry out and do not leave." According to the two latter renderings, the clause is a mere solemn confirmation of the previous promises.