What is or is not biblical regarding a pre-marital agreement for handling money and possessions in the event of a separation or divorce?
"And He answered and said to them, "Have you not read that He who made them at the beginning 'made them male and female,' and said, 'For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one flesh'? So then, they are no longer two but one flesh. Therefore what God has joined together, let not man separate"" (Matthew 19:4-6).
A prenuptial agreement is a plan for how to separate before a couple even tries to become one. It keeps some or all of what one person has out of the hands of the other -- just in case. Thus it interferes with a full commitment to become one.
Marriage is not a temporary commitment. It is a permanent one. It is a vow before the Lord to take another human being as your spouse. Are you sincere saying, "for as long as we both shall live," if you have made exit plans in advance? "For the woman who has a husband is bound by the law to her husband as long as he lives" (Romans 7:2).
"For the LORD God of Israel says that He hates divorce, for it covers one's garment with violence," says the LORD of hosts. "Therefore take heed to your spirit, that you do not deal treacherously" (Malachi 2:16). A divorce means one or both in the marriage has sinned, violating the terms of the covenant freely made. Does a person plan in advance to sin?
"Now to the married I command, yet not I but the Lord: A wife is not to depart from her husband. But even if she does depart, let her remain unmarried or be reconciled to her husband. And a husband is not to divorce his wife" (I Corinthians 7:10-11). Divorce ought to be a rare event that is done in extreme circumstances where the other person has violated the terms of the covenant made so badly that measures need to be taken temporarily until the issue is resolved. Even in divorce, a person is still bound by the terms of the marriage covenant -- they cannot marry another. But extreme emphasis is placed on not divorcing. And even in the rare case where divorce happens, the emphasis is on making it possible for the two to reconcile. The only exception is when a spouse commits sexual sin (fornication). "And I say to you, whoever divorces his wife, except for sexual immorality, and marries another, commits adultery; and whoever marries her who is divorced commits adultery" (Matthew 19:9). Even here, I don't think the Lord is meaning a one time sin but a spouse who continues unrepentant in fornication.
Marriage is a serious matter, not to be taken lightly. If you won't marry someone without a prenuptial agreement, then that tells me that you don't fully trust the one you claim to love. Love "bears all things, believes all things, hopes all things, endures all things. Love never fails" (I Corinthians 13:7-8). A prenuptial agreement means you are entering a marriage with the idea that there may be problems in the future that cannot be resolved. If such is the case, you shouldn't be marrying that person.