What is the legal ruling regarding a wife and her sister observing hijab in front of their friend's 10-year-old son, and to what extent is niqab obligatory in this situation?

The jurists have stipulated that a woman is not obliged to cover herself from an indiscriminating child. As for a discriminating child who has not yet reached adolescence, some jurists hold that he is like a mahram in terms of viewing, meaning he is permitted to see what is typically exposed, such as the neck, head, hands, and feet.

However, if the child approaches puberty (adolescence), the woman must veil herself from him, especially given children's awareness of matters of desire in this era. The questioner's opinion is correct regarding his wife's obligation to veil herself from the ten-year-old child, and she must obey him in this. He should also advise her sister to veil herself from him, while it is not recommended for him to sit with them at this age.

As for wearing the niqab, scholars have differed on its obligation if fitna (temptation) is assured not to occur. However, it is obligatory if leaving it causes fitna, and it is a means of chastity and protection for women.