If men dont have protective jealousy over their wives then take this as a warning...
The prophet Muhammad saw said 'A Dayooth will not enter Jannah.' The Sahabah asked, 'Who is a Dayooth?' Rasoolullah sallallahu alaihe wasallam said, 'A man who does not care who visits his wife (i.e. men).'
And on the issue of Ghayrah, Ibn al-Qayyim, rahimahullaah, said,
"And the Dayyouth (the man with no jealousy over the women in his family) is the most vile of Allah's creation, and Jannah is forbidden for him, (because of his lack of Ghayrah - jealousy).
The foundation of the Religion is Ghayrah, and the one without Ghayrah is one without Religion, for Ghayrah protects the heart and enlivens the limbs, and shields one from evil and lewdness, and lack of Ghayrah kills the heart so that the limbs die, so that there remains not even shielding from [the minor things].
And the example of Ghayrah in the heart is the example of the strength that shields one from sickness and fights it off, so if the strength leaves, he will be faced with the sickness, and will not find any thing to protect himself from it, so it will establish itself [within him] and destroy him ."
Ad-Daa' Wad-Dawaa', p.77