Is a husband sinful if he engages in sexual activity with his first wife via video call in the second wife's bedroom, without any regard for the second wife's presence?

A man is obligated to be fair between his wives in the division (of nights), by assigning a night to each wife or according to what they agree upon. It is not permissible for the husband to go to a wife who is not assigned her turn at night except out of necessity, nor during the day except out of need. Furthermore, sexual intercourse is not permissible in either case. However, entering upon a wife who is not assigned her turn during the day for a need is permissible, provided it is not prolonged and does not involve sexual intercourse. As for engaging in sexual activity with another wife via video, if it leads to ejaculation, it is considered in the same category as the prohibited intercourse with a wife who is not assigned her turn, due to the resulting decline in his activity regarding the right of the wife whose night it is. The husband should be advised to be just and to beware of injustice.