All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
Enjoying one’s wife when she is in menses between the navel and the knee– without penetration in the vagina or anus – is a matter upon which the scholars differed about its ruling; the view we consider (here in Islamweb) to be the preponderant one is that it is permissible.
Inserting the finger into the vagina of a menstruating woman is not permissible because it involves touching impurity without necessity.
Nonetheless, if the finger is covered with something, like gloves, that prevents touching the impurity, then we have not come across any statement of the scholars in this regard. It appears – Allah knows best – that it is not forbidden according to the view that we consider to be the preponderant one, that it is permissible to enjoy a menstruating woman with the exception of having intercourse in the vagina.
However, if it is proven that this act harms the wife, then it becomes prohibited because of the harm.
In any case, we recommend to avoid this act in order to be on the safe side and avoid potential harm.
Allah knows best.