Christian author Joshua Harris appears to be kissing his marriage goodbye.

Harris, who authored "I Kissed Dating Goodbye" in 1997 and "Boy Meets Girl: Say Hello to Courtship" in 2000 that helped shape purity culture for many millennial believers, announced Thursday he was "separating" from Shannon, his wife of 20 years. He said on Instagram the two "will continue our life together as friends."

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The former pastor of Covenant Life Church in Gaithersburg, Md., announced the split was due to "significant change [that] have taken place in both of us."

"It is with sincere love for one another and understanding of our unique story as a couple that we are moving forward with this decision," Harris wrote. "We hope to create a generous and supportive future for each other and for our three amazing children in the years ahead."

The two asked for understanding and respect for privacy during the "difficult time."

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Reactions to the news ranged from disbelief to anger to sympathy and prayers.

Harris' book was a bestseller and he became an influential voice on sex and relationships. His book argued that God wanted people to be pure on their wedding day and that the restraint led to a happy marriage.

But years later, there was a backlash after Christians who followed the book's advice ended up in miserable marriages. Harris ended up apologizing for the "harm" his book caused.

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"To those who read my book and were misdirected or unhelpfully influenced by it, I am sincerely sorry," Harris said in a statement. "I never intended to hurt you. I know this apology doesn’t change anything for you and it’s coming too late, but I want you to hear that I regret any way that my ideas restricted you, hurt you, or gave you a less-than-biblical view of yourself, your sexuality, your relationships, and God."

He discontinued his book's publications even though he said many were also helped by it.