many wives or husbands

Question from Cristal on 2/20/2008:  
Having many wives or husbands or cheating on your spouse is called adultery and i know its a mortal sin but the other day i was reading the bible and it said that abraham had a wife named sarah and she couldnt have children so she told abraham to make a baby with her servant and he did and i kept reading further and realized that many people in the bible had commited adultery and my question is this, if today having many wives or cheating on your spouse is called adultery and its a mortal sin and god doesnt like us comitting adultery than why back when abraham and his decendents were around why wasnt it a mortal sin and why didnt god tell them not to do it if its so bad ,why were they allowed to do it and not told its bad?
Answer by Fr. John Echert on 2/21/2008: 
The practice of polygamy of the Patriarchal period of the Old Testament was not the ideal but it was not adultery, that is marital unfaithful, as such. The intent of the situation you describe was to allow a descendant to be born of the line of Abraham through the servant girl, who was serving as a sort of surrogate mother for Sarah, who was beyond the normal years of conception. Still, God did not plan to achieve his promise in this deficient manner and Sarah herself later conceived by her husband. Polygamy as well as divorce and remarriage were tolerated by God for a time, in the Old Testament, but Jesus re-established the original order of creation when he commanded one husband and wife in an inseperable union of marriage.

So was the action of Abraham a sin? The Church Fathers would not regard it a mortal sin, but venial at most, and certainly short of the ideal and original order.

Thanks, Cristal

Father Echert