Moses was given permission from the Lord in the OT to grant divorces due to the hardness of hearts. We Christians live under the NT covenant which states....
"And unto the married I command, [yet] not I, but the Lord, Let not the wife depart from [her] husband: But and if she depart, let her remain unmarried, or be reconciled to [her] husband: and let not the husband put away [his] wife." (1Cr7:10-11)
Christians are commanded not to depart, but if one does depart, we are not given any liberty to remarry another. We are to remain unmarried or reconcile to your spouse.
By permission Paul states (not the Lord) that if a Christian has found themselves married to an unbeliever and the unbeliever departs, this Christian is not bound to this marriage and therefore could remarry, a believer of course (2Cr6:14).
"But to the rest speak I, not the Lord: If any brother hath a wife that believeth not, and she be pleased to dwell with him, let him not put her away. And the woman which hath an husband that believeth not, and if he be pleased to dwell with her, let her not leave him............But if the unbelieving depart, let him depart. A brother or a sister is not under bondage in such [cases]: but God hath called us to peace." (1Cr7)
IF the unbeliever departs from the believer, the other party freed remaining freed to remarry, BUT has to be to fellow christian!
IF there is a "biblical divorce" advice is to stay single, BUT God allows the offended party to remarry in the Lord...
IF just a divorce, stay seperated, but IF other remarries, no longer bound by Marriage, can remarry in the Lord...
So Bible allows remarriage, just depends on each situation!
And Paul writing it same as if Jesus said it!