Desiring God author John Piper is baffled by Christians who marry non-believers.
In a recent blog post, Piper said it was "inconceivable" and "incomprehensible" to him for a Christian to marry someone who is not a fellow Christian.
He called it an act of defiance that "shows how deeply compromised the believer's love for Christ is."
"How can the heart of a believer embrace Jesus as its supreme treasure and satisfaction, and reject the words of Jesus in order to be in the arms of one who has no faith and no true affection for the believer's most treasured possession?" he said, adding, "Something is deeply, deeply wrong with the heart's affection for Christ."
He argued that Christians who enter into mixed marriages have "compromised" their love for Christ and are "defying and rebelling against an explicit command of the New Testament of God" found in 1 Corinthians 7:39.
"So, if this teaching is made clear to the believer, and the believer rejects obedience to this command, she or he is acting in open defiance of the teaching of the apostles and of God," he said.
Piper went as far as to say that Christians in mixed marriages should be excommunicated from the church in order "to sober the disobedient believer, wake them up, and win them to a repentant and obedient heart and restoration."
"Many people do not take the Bible seriously," he said.
"They are baffled and angry by churches who take the Bible as seriously as I'm saying. Many professing Christians today would regard such excommunication as more hurtful than helpful.
"They call it intolerant; they even call it hateful. But that's because they elevate their own wisdom above God's wisdom."