Warning to the one who separates 

The one who tries to bring seperation between husband and wife is an ally of Shaytaan 

The Messenger of Allah (Sallallahu alayhi wa sallam) said; 

"Iblis (the head of the shayateen or Satan) places his throne upon water and then sends his detachments (those who work under him) for creating Fitnah (dissension) and the closest to him is the one that creates most Fitnah. 
One of them comes and says; I did such and such and Iblis replies, you have not done anything and so on. Then one comes and says 'I did not spare so and so until I sowed the seed of discord between a husband and wife (and caused them to be seperated). Iblis then goes near him and says, "You have done well"

From this Hadith we see that Iblis doesn't like any Fitnah more than the Fitnah of seperation between husband and wife. A single fight sowed between the husband and wife or misunderstandings arising in marital relations disturbs the whole family. The most affected by it after the spouses are the children who feel disturbed due to fights and arguments. Their nurturing becomes heavily lacking of serious efforts from both spouses because of their own negativities. Even existing love between husband and wife can turn into dislike and many cases, hatred, which gives immense pleasure to the Shaytaan. In many cases, the ones who cause fights are none other than our own close ones and family members but we do not suspect them because we believe they will not wish harm for us, but Shaytaan does not leave anyone out of his trap. 

So O the one who helps in causing fights and discord between husband and wife, know that you are on the path of Shaytaan which leads to nothing but hellfire. And those who make this act a habit of theirs are not only allies of Shayateen but are removed from the mercy of Allah after which anything the like of it or worse can also occur with them . 

Those who even wish for such things to occur should remember that doing such things not only ruin their Aakhirah and hereafter but also creates chances for their Dunya to be destroyed because we not only receive punishment for it in the hereafter but Allah also brings such situations for us in this Dunya to have a taste of our own doings.