Zacharias Became Mute Because He Didn’t Believe Until He Did Believe

11 And there appeared unto him an angel of the Lord standing on the right side of the altar of incense. 12 And when Zacharias saw him, he was troubled, and fear fell upon him. 13 But the angel said unto him, Fear not, Zacharias: for thy prayer is heard; and thy wife Elisabeth shall bear thee a son, and thou shalt call his name John. 14 And thou shalt have joy and gladness; and many shall rejoice at his birth. 15 For he shall be great in the sight of the Lord, and shall drink neither wine nor strong drink; and he shall be filled with the Holy Ghost, even from his mother's womb. 16 And many of the children of Israel shall he turn to the Lord their God. 17 And he shall go before him in the spirit and power of Elias, to turn the hearts of the fathers to the children, and the disobedient to the wisdom of the just; to make ready a people prepared for the Lord. 18 And Zacharias said unto the angel, Whereby shall I know this? for I am an old man, and my wife well stricken in years. 19 And the angel answering said unto him, I am Gabriel, that stand in the presence of God; and am sent to speak unto thee, and to shew thee these glad tidings. 20 And, behold, thou shalt be dumb, and not able to speak, until the day that these things shall be performed, because thou believest not my words, which shall be fulfilled in their season. 21 And the people waited for Zacharias, and marvelled that he tarried so long in the temple. 22 And when he came out, he could not speak unto them: and they perceived that he had seen a vision in the temple: for he beckoned unto them, and remained speechless. 23 And it came to pass, that, as soon as the days of his ministration were accomplished, he departed to his own house. 24 And after those days his wife Elisabeth conceived, and hid herself five months, saying, 25 Thus hath the Lord dealt with me in the days wherein he looked on me, to take away my reproach among men. 

(From Luke 1 KJV)