The Archangel Gabriel Appears to Zachary the Musée Condé, Chantilly.
SCRIPTURE COMMENTARY #2
The power of persevering prayer: Zachary and Elizabeth had probably prayed for many years that they might have a son. Their prayers seemed to be offered up in vain, but nevertheless they persevered in laying the great desire of their hearts before God. At last they were heard, and received from God much more than they had asked for. They had asked for a son who might succeed his father in the priestly office, and they received a son who was to become a great Saint, a prophet of God, and the precursor of the Divine Redeemer. This was the rich reward of their perseverance in prayer.
[From 'A Practical Commentary on Holy Scripture' by Bishop Knecht, D.D.]
(1899 Douay-Rheims Bible)