(Nur-uth-Thaqalayn...
Imam Sadiq (a.s.) said that fasting was not only an abstinence from eating and drinking, and then he recited the verse under discussion. In this holy verse, Allah, the Pure, commands Mary to eat from that delicious and nutritive food and to drink from that wholesome water.
The verse says: " So eat and drink …" She was also commanded to refresh her eye by that newly born child and not to be worried about the future; and if anybody asked her regarding it, she would say by sign that she had kept fasting (a silence fasting) for Allah, the Beneficent, and that was why she could speak with no one.
The verse continues saying: " …and refresh your eye; and if you meet any mortal, say: 'Verily I have vowed a fast to the Beneficent (God), so never shall I speak today with any human being'." Therefore, she should have peace of mind from any points of view and should not let herself be grievous and sad.
From the text of the verse, it is understood that the fast of silence was something familiar to that community, so they did not object to it however this kind of fasting is not sanctioned in the religion of Islam.
It is narrated from Imam Ali-ibn-il-Hussayn (a.s.) who said: "A fast of Silence is prohibited." Ali-ibn-Abitalib (a.s.) has narrated from the Prophet of Islam (p.b.u.h.) who said: "The first thing that a woman may eat after her delivery must be fresh dates." Some Islamic traditions denote that the best food for a pregnant woman, and her drug, is fresh dates.