Whereby shall I know this? - The thing was improbable, and he desired "evidence" that it would take place. The testimony of an "angel," and in such a place, should have been proof enough; but people are slow to believe the testimony of heavenly messengers. As a consequence of not believing, he was struck mute.

Whereby shall I know this? - All things are possible to God: no natural impediment can have any power when God has declared he will accomplish his purpose. He has a right to be believed on his own word alone; and it is impious, when we are convinced that it is his word, to demand a sign or pledge for its fulfillment.

And Zacharias said unto the angel, whereby shall I know this?.... Notwithstanding such an appearance of an angel to him, which in those times was not so usual, and this in the holy place; and the things themselves which were told him, and these as the return of prayer; yet he distrusted, and wanted a sign, whereby he might know the truth of them, as the Jews were generally desirous of, and as the father of them was; who expressed himself in much such language, on a certain occasion, as this his son did; see Genesis 15:8.

For I am an old man; at least sixty years of age; for with the Jews, sixty years were reckoned, "for old age" (w); and a man of these years, was accounted an old man: and the Jewish Rabbins observe (x), that the word for old age in Job 30:2 is by "gematry, sixty"; that is, the letters of the word, numerically make so much. The Mahometan writers, as before observed on Luke 1:7 make him to be ninety nine years of age: he was not discharged from service; the Levites were at fifty, but not the priests; blemishes, as the Jewish writers say (y), made them unfit for service, but years did not: and even the law concerning the Levites, they say (z), only respected the time they carried the sanctuary from place to place, and not future generations; and that they are disqualified neither by blemishes, nor by years, only by voice, for singing of the song; but then they might be among the porters; so that they were not on that account laid aside from all service:

and my wife well stricken in years. The Mahometan writers, as before, say, she was "eighty nine"; a like objection Abraham made, though he afterwards got over it, and was strong in faith, giving glory to God, believing in his power and faithfulness; see Genesis 17:17.

(w) Misn. Abot, c. 5. sect. 21. & Maimon. in ib. (x) R. Sol. Urbin. Ohel Moed, fol. 24. 2.((y) T. Bab. Cholin, fol. 24. 1.((z) Maimon. Hilch. Cele Hamikdash, c. 3. sect. 8.

Whereby (κατὰ τί)

Lit., according to what? It demands a standard of knowledge, a sign.

For

I require a sign, for I am old.

And Zacharias said unto the angel, Whereby shall I know this? for I am an old man, and my wife well stricken in years.

1:18 By what shall I know this? He wanted a sign.

1:18 Zacharias said, Whereby shall I know this? - In how different a spirit did he blessed virgin say, How shall this be? Zacharias disbelieved the fact: Mary had no doubt of the thing; but only inquired concerning the manner of it.

18. Whereby, &c.-Mary believed what was far harder without a sign. Abraham, though older, and doubtless Sarah, too, when the same promise was made to him, "staggered not at the promise of God through unbelief, but was strong in faith, giving glory to God." This was that in which Zacharias failed.

1:5-25 The father and mother of John the Baptist were sinners as all are, and were justified and saved in the same way as others; but they were eminent for piety and integrity. They had no children, and it could not be expected that Elisabeth should have any in her old age. While Zacharias was burning incense in the temple, the whole multitude of the people were praying without. All the prayers we offer up to God, are acceptable and successful only by Christ's intercession in the temple of God above. We cannot expect an interest therein if we do not pray, and pray with our spirits, and are not earnest in prayer. Nor can we expect that the best of our prayers should gain acceptance, and bring an answer of peace, but through the mediation of Christ, who ever lives, making intercession. The prayers Zacharias often made, received an answer of peace. Prayers of faith are filed in heaven, and are not forgotten. Prayers made when we were young and entering into the world, may be answered when we are old and going out of the world. Mercies are doubly sweet that are given in answer to prayer. Zacharias shall have a son in his old age, who shall be instrumental in the conversion of many souls to God, and preparing them to receive the gospel of Christ. He shall go before Him with courage, zeal, holiness, and a mind dead to earthly interests and pleasures. The disobedient and rebellious would be brought back to the wisdom of their righteous forefathers, or rather, brought to attend to the wisdom of that Just One who was coming among them. Zacharias heard all that the angel said; but his unbelief spake. In striking him dumb, God dealt justly with him, because he had objected against God's word. We may admire the patience of God towards us. God dealt kindly with him, for thus he prevented his speaking any more distrustful, unbelieving words. Thus also God confirmed his faith. If by the rebukes we are under for our sin, we are brought to give the more credit to the word of God, we have no reason to complain. Even real believers are apt to dishonour God by unbelief; and their mouths are stopped in silence and confusion, when otherwise they would have been praising God with joy and gratitude. In God's gracious dealings with us we ought to observe his gracious regards to us. He has looked on us with compassion and favour, and therefore has thus dealt with us.