In Ezra, they start rebuilding the Temple, and they discover that there are actually a number of Israelites that have taken foreign wives. Ezra falls to his knees and prays for his people and the people repent and turn from their ways.
But how does this show itself?
3 Therefore let us make a covenant with our God to put away all these wives and their children, according to the counsel of my lord  and of those who tremble at the commandment of our God, and let it be done according to the Law. 4 Arise, for it is your task, and we are with you; be strong and do it.” 5 Then Ezra arose and made the leading priests and Levites and all Israel take oath that they would do as had been said. So they took the oath.And this is really interesting on a theological basis. Here's what I'm thinking -
1) It seems clear that this act is one that is pleasing to God. Not only is it a time of congregational repentance and confession of sin, but they decide to make a covenant before the Lord, very similar to other cases where this happens and the people repent of their wicked ways and make a covenant to follow him, or to obey his laws, etc. On top of that, v.3 says that they do this "according to the counsel of my lord."
2) It also seems clear that "put away" is not just a "don't look at these people," but an active casting off and shunning, aka divorce. This was all to be done "according to the Law." The only examples I can think of in the Law are those of a husband, writing his wife a certificate of divorce. Additionally, if we do a search on the phrase "put away," we find it used in the putting away of household gods to truly serve the Lord. I find no conception of this actually allowing for a "keep them around but just have nothing to do with them."
Now, this does pose some difficulties, for Paul actually writes in 1 Corinthians that if a man finds himself married to an unbeliever who is willing to stay, they should stay together (1 Cor. 7:12).
A couple possibilities, all of them don't quite satisfy me now, but here are some possibilities.
1) We can weaken the phrase "put away" to allow for "remain married, but don't be drawn away from them." I don't like this idea because it seems to go against the seriousness of the sin. Surely if that was the solution, it isn't that bad. But it seems like it's a serious act, one that takes 2 and a half months to completely resolve (Ezra 10:16-17).
2) It may be possible that this case is not covered by Paul's interpretation of the marriage covenant in 1 Corinthians 7, namely, these people, as Israelites, ought not to have married these foreign women, and thus they were obligated to divorce them. That would make a modern day analogy if a believer marries a non-believer, he ought to divorce her. That's a difficult statement to believe, especially because of Paul's statement that if the unbeliever consents to stay together, they ought to stay. It doesn't seem to say "if you were both unbelievers but then one of you was converted (though, that is the expected cause)."
Whatever our interpretation, it does seem that the passage teaches the seriousness of marriage and how important it was. Picking who we marry is not some trivial act, but one that should be taken with great trepidation and a holy fear of the Lord. It also demonstrates just how far sometimes we must go to be obedient to the Lord, even at the cost of our wife if she is leading us away from the love of God. We must put away our wives lest we put away the Lord. Could this be akin to chopping off our hand lest we be cast in the fires of hell?