Strengthen you the weak hands, and make firm the feeble knees.
All Commentaries on Isaiah 35:3 Go To Isaiah 35
Ambrose of Milan
AD 397
Then let us flee the wickedness of this world, in which “the very days are evil,” and flee it relentlessly. On that account Isaiah cries out, “Be strong, you hands which are feeble and you knees which are without strength.” This means: Be strong, you knees, not of the body but of the soul, so that the footstep of the spirit can rise up straightway to the heights of heaven. Thus conduct will be more stable, life more mature, grace more abundant and discretion more guarded.