This is an exhortation, not to others, but to himself. His stronger self exhorts his weaker self not to despair, but to wait upon God and, meanwhile to be of good courage; or, be strong as the phrase is elsewhere generally translated. "Be strong," he says to himself, and he (God) shall strengthen thine heart. Make an effort to be strong, and the strength will be given thee, as thou makest it. Then in this strength, thus given, continue till waiting - Wait, I say, on the Lord.
- Pulpit Commentary
