Is it permissible to refrain from shaking the hand of the wife's mother due to her beauty and the fear of temptation, even though she is a mahram, and what misunderstandings might result from this refusal?

The wife's mother is a mahram to the husband, and it is permissible for him to be in seclusion with her and to shake her hand, as long as there is no fear of fitna (temptation) or lust. Otherwise, it is forbidden. Al-Sarakhsi said: "Touching and looking are only permissible if one is safe from lust for himself and for her. But if he fears lust for himself or for her, then it is not permissible for him." Al-Baji said: "There is no dispute regarding the prohibition of looking [at any mahram] with the intention of pleasure or enjoyment."