We must first understand that Zechariah being struck dumb need not be taken as a great punishment from God. Rather, we should take it as a sign given by the angel that Zechariah, in his old age would be getting a son. In the Old Testament, even individuals, who were believers, have asked for a sign to know the truth of the matter. These signs are not considered as punishment. God said to Abraham that he would be giving the land of Canaan as his inheritance. Then, like Zechariah, Abraham also asked how this could happen (Gen 15:7-13). God gave Abraham a sign without punishing him (Gen 15:7-16). Gideon too asked God for a sign that he would be the instrument to regain Israel. God then gave the sign of the fleece covered with snow (Judg. 6:37-38). Hezekiah asked for a sign to know he would be healed. As a sign the shadow of Ahaz' sundial moved ten ft. backwards(2 Kings 20:8-11). God gave signs so that the people might believe Moses. For example, the rod that became a snake, the breast that was stricken with leprosy (Ex 4:1-9). In Isaiah 7:11 God himself tells Ahaz to ask for a sign.
In the matter of "vocation" that is, the call of God recorded in the Old Testament, we do not see signs as something sent to punish the person. We should, therefore, take the muteness of Zechariah more as a sign than as a punishment. Luke has stated in 1:6 that Zechariah was a righteous man and one who obeyed God's laws and commandments. The Good News given to Zechariah is of the same pattern of God's election as seen in the Old Testament. The call of Abraham (Gen 15:1-16), the apocalypse in the book of Daniel (chapters 7,8,9,10) and the revelation given to Zechariah are parallels. We can see in the book of Daniel the man of God who lost his power of speech in the presence of God (Dan 10:15). "While he was speaking these words to me, I turned my face toward the ground and was speechless" (Dan 10:15). In Luke 1:22 the people understand muteness as a sign of receiving the revelation of God. Also Zechariah was struck dumb so that the divine revelation he received might not be announced before the time fixed for it.
Zechariah's muteness can be taken as a punitive sign too. Similar signs and wonders can be seen in Luke's Book of the Acts. (for example, Acts 1:18;5:5-10;12: 23; 13:11). The punishment Zechariah received was a light one. For he was dumb only for a short time. In the Greek Bible the word for lifelong muteness is "Kophos". Zechariah was dumb only temporarily. For this muteness Lk 1:20 of the original Greek uses the word "Siopen"(silent). We can understand the temporary punishment that Zachariah received and his lack of faith in the following manner.
The annunciation to Zechariah and to Mary (Lk 1:5-25;1:26-38) are written as an antithetic parallelism. In this parallelism Jesus and Mary who are the initiators of the New Covenant are seen as being more glorious than Zechariah and John. If Zechariah, who belonged to the Old Covenant, does not believe and is punished, Mary the mother of Jesus, the initiator of this New Covenant believes and surrenders to God's will. The evangelist is here pointing out through an antithetic parallelism that the New Covenant is more sublime than the old.
Zechariah's words were not a request to stabilise his faith. He rejected the words of the angel as an impossibility. He spoke as if he could not believe this at all. We can even say he was scandalised by the angel's words. Zechariah doubted the truth of the message, whereas, Mary did not question the veracity of the angel's words. She did not ask for a sign as evidence of the truth of his words. She only asked more questions in order to understand the angel's words still better. She believed that what the angel told her would take place. But she did not know how it would happen. If we examine the Greek root of Mary's words, we will find they do not indicate any doubt. It is only a question inspired by the great wonder of the Good News, hitherto never heard of, that we find in Luke 1:34. Mary could never think of a pregnancy before marriage. She, therefore, wonders about it and asks how it could take place.
According to some scholars the reason why Zechariah was punished is because he was a priest. Zechariah was well versed in the Old Testament. In the light of salvation history he should have believed the words of the angel. A priest should never have forgotten the miraculous gift of children given in old age to people like Abraham, Sara, Elkana and Hannah. In this Zechariah erred more than a village girl like Mary. Since the ancients lived in the early stage of God's revelation God gave them signs that were not punitive. But behind Zechariah was a long history of God's boundless power and miraculous manifestations. For this reason he had the duty and responsibility to believe in God's word in a greater measure.
In the New Testament Jesus
visualises and praises believers who do not need signs and wonders (Lk
11:29-30; Jn 20:29). Great things happen to the believer who, like Mary,
says, "Behold the handmaid of the Lord" and with all his heart relies on
God and believes in his words because nothing is impossible to God (Lk
1:37). The parable of the rich man and Lazarus makes it clear that signs
and wonders do not save a man (Lk 16:19-31). Those who do not listen to
the word of God (those who do not obey Moses and the prophets) will not
believe even if someone rises from the dead (Lk.16:28-31). This truth is
relevant even today.