When they are united in their couplings, with the sanctification of marriage and the 7 blessings, which are their unity, in sanctity and in blessing, it is stated of them: Do not take the mother upon the children... (Deut. 22:6) but if not, then You shall surely send away... (Deut. 22:7)
And Israel, they are in exile, in the ‘other’ domain, for when they do not unite in their couplings, with the rites of sanctification and the 7 blessings, which are their unity in sanctity and blessing, then instead of holiness – impurity resides upon them, and instead of blessing – cursing resides upon them, and instead of unity – separation resides upon them.