Is it permissible to conceal one's voluntary fasting from family members such as one's wife, mother, or sister? And how should a fasting person act if invited to eat or drink while observing a voluntary fast?

It is recommended to conceal acts of obedience, such as fasting, unless there is a need to reveal them. However, when invited to a meal, there is no harm in revealing one's fast, as the Prophet, peace and blessings be upon him, said: "If one of you is invited to a meal while he is fasting, let him say: 'I am fasting.'" Imam An-Nawawi is of the opinion that saying "I am fasting" serves as an excuse, and if he is permitted to be absent, his attendance is waived. If he is not permitted, he is obliged to attend, but he is not obliged to eat. It is permissible to reveal supererogatory acts of worship when there is a need for it; otherwise, it is recommended to conceal them.