He said, "My Lord, make for me a sign." He said, "Your sign is that you will not [be able to] speak to the people for three days except by gesture. And remember your Lord much and exalt [Him with praise] in the evening and the morning."
The Supplication of Zakariyya, and the Good News of Yahya's Birth
When Zakariyya saw that Allah provided sustenance for Maryam by giving her the fruits of winter in summer and the fruits of summer in winter, he was eager to have a child of his own. By then, Zakariyya had become an old man, his bones feeble and his head full of gray hair. His wife was an old women who was barren. Yet, he still supplicated to Allah and called Him in secret,
رَبِّ هَبْ لِى مِن لَّدُنْكَ
(O my Lord! Grant me from Ladunka,) from You,
ذُرِّيَّةً طَيِّبَةً
(A good offspring) meaning, a righteous offspring,
إِنَّكَ سَمِيعُ الدُّعَآءِ
(You are indeed the All-Hearer of invocation.) Allah said,
2. With reference to verse 41, Sayyidna Zakariyya's purpose behind requesting a sign (of pregnancy) was to be happy at the prospect and thus be enabled to show their gratitude all along even prior to the actual birth of the child. So, Allah gave him the sign stated above.
The sign given was remarkably suitable to its purpose. His request for a sign was prompted by his wish to show his gratefulness. Now, the sign set for him leaves him incapable of doing anything but this. Even a hundred signs would have not done what this one sign did and, of course, the noble purpose he had on his mind was all too well-accomplished. (Bayn al-Qur'an)
The last phrase: (except through gestures) in this verse tells us that in a situation where speech is not possible because of a valid reason, gesture would be deemed as its substitute. Consequently, it appears in a hadith that the Holy Prophet ﷺ asked a maid-servant: این اللہ ؟ I ('Where is Allah?' ). She pointed out towards the sky. He said: 'This maid-servant is a Muslim.' (al-Qurtubi)
Tazkirul Quran
Maulana Wahiduddin KhanOn ayahs 32–43
It is a psychological reality that one who loves someone cannot at the same time love the enemy of the beloved. It is also a fact that when the beloved is a Being who has the status of one’s Creator and Sustainer, then this love will necessarily bring about in the lover the desire to obey that Being in all matters. If the love of God does not produce in him feelings of obeisance to Him, then such a love is false. A believer who is one in name only will be included among the deniers. God Himself has testified to the Prophet’s total obedience to Him in all matters. So the authentic example of a life of God-worship in this world is only such as was handed down to us by His messenger.
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.