Praise be to Allah.
If the iddah (waiting period following divorce) of a revocably-divorced wife ends, she becomes a stranger to the husband like any other women who are not related to him; it is not permissible for him to touch her, look at her or be alone with her, and if she gets married to another man, the matter becomes more serious and more abhorrent.
Based on that, so long as your husband has not done a marriage contract with this woman, what he is doing of embracing her, touching her or kissing her is one of the gravest of evil actions. We do not know how any Muslim can do such a thing. If he has decided to marry her, how can he not have any patience to avoid what is haraam, until she becomes permissible to him?! We ask Allah to keep us safe and sound. If this woman is still married to her (current) husband or he has divorced her but she is still in the iddah (waiting period), then it is even more serious and more abhorrent, as stated above, and she is betraying her husband.
Whatever the case, what your husband is doing with this woman is blatant immorality and it is a kind of zina (adultery). Zina is of varying degrees, some of which incur the hadd punishment, namely intercourse in the vagina, and some are less serious than that, such as looking, touching and so on. But all of them are haraam and one leads to the other, darkness upon darkness. We ask Allah to keep us safe and sound by His grace. Al-Bukhaari (5744) and Muslim (4801) narrated from Abu Hurayrah that the Prophet (blessings and peace of Allah be upon him) said: Allah has decreed for the son of Adam his share of zina which he will inevitably fall into. The zina of the eyes is looking, the zina of the tongue is speaking, the nafs (self) wishes and longs, and the private part confirms that or denies it.
And he (blessings and peace of Allah be upon him) said: Any woman who takes off her clothes anywhere but in her husband's house, has torn the screen that was between her and Allaah.
Narrated by Ibn Maajah, 3750; classed as saheeh by al-Albaani
If your husband is encouraging this woman to get divorced from her (current) husband so that she can go back to him, then he has fallen into another sin, which is ruining her and spoiling her for her husband. It was narrated that Abu Hurayrah (may Allah be pleased with him) said: The Messenger of Allah (blessings and peace of Allah be upon him) said: He is not one of us who turns a woman against her husband or a slave against his master. Narrated by Abu Dawood, 2175; classed as saheeh by al-Albaani in Saheeh Abi Dawood.
Abu Dawood also narrated (5170) that Abu Hurayrah (may Allah be pleased with him) said: The Messenger of Allah (blessings and peace of Allah be upon him) said: Whoever turns a man's wife or slave against him is not one of us. Classed as saheeh by al-Albaani in Saheeh Abi Dawood.
Shaykh Abd al-Azeem Abaadi (may Allah have mercy on him) said: Whoever turnsâ¦ against means whoever deceives and corrupts.
a woman against her husband by mentioning the husband's bad qualities in front of his wife, or the good qualities of another man in front of her.
End quote from Awn al-Mabood, 6/159
And he said: Whoever turns a man's wife against him means ruining and corrupting her, or making the idea of divorce seem good to her, so that he could marry her or someone else can marry her, and so on.
Awn al-Mabood, 14/52
Some scholars are of the view that if a man turns a woman against her husband, it is permanently haraam for him to marry her, and his marriage to her is not valid.
See the answer to question no. 84849
To sum up, what your husband is doing in front of you is a great evil, and it is not permissible for you to approve of it or keep quiet about it, let alone take part in it. What you have to do is exhort your husband and advise him, and explain to him that what he is doing is abhorrent and haraam. If he stops, then praise be to Allah, but if he persists in this action it is not permissible for you to be present when this evil is being committed. You can threaten to expose him and disclose what he is doing. Then if he persists in that, it is permissible for you to ask for a divorce, because of his evildoing and sin.
Being together with two wives in one bed is permissible subject to three conditions: