17 A wicked messenger falleth into mischief: but a faithful ambassador is health.
Here we have,
1. The ill consequences of betraying a trust. A wicked messenger, who, being sent to negotiate any business, is false to him that employed him, divulges his counsels, and so defeats his designs, cannot expect to prosper, but will certainly fall into some mischief or other, will be discovered and punished, since nothing is more hateful to God and man than the treachery of those that have a confidence reposed in them.
2. The happy effects of fidelity: An ambassador who faithfully discharges his trust, and serves the interests of those who employ him, is health; he is health to those by whom and for whom he is employed, heals differences that are between them, and preserves a good understanding; he is health to himself, for he secures his own interest. This is applicable to ministers, Christ’s messengers and ambassadors; those that are wicked and false to Christ and the souls of men do mischief and fall into mischief, but those that are faithful will find sound words to be healing words to others and themselves.
– Matthew Henry Commentary