David takes official and calculated steps to reclaim his wife, Michal. The timing of this demand is strategic. Having just secured the crucial backing of Abner, David finally feels secure enough to make his move [מצודת דוד, ביאור שטיינזלץ]. Yet, rather than bypassing the current leadership and relying solely on Abner's power, David approaches Michal's brother, Ish-bosheth, directly. This is a deliberate show of respect, as David refuses to take Michal away without her brother's formal permission [רד״ק].
When making his demand, David specifically highlights the unique and dangerous price he paid for his bride: one hundred Philistine foreskins. This detail serves a dual purpose. From a legal standpoint, Saul had previously tried to invalidate the marriage by claiming it was based on a financial debt. By mentioning the physical items he brought, David clarifies that the marriage was enacted through the objects themselves rather than a monetary loan, proving that Michal is still his lawful wife [מלבי״ם, רד״ק]. On a more practical level, bringing up this feat reminds Ish-bosheth that David risked his very life to win Michal. It serves as a firm justification for her return and carries a subtle warning that David is fully prepared to fight for her once again [רד״ק, מצודת דוד]. Interestingly, while David had actually delivered two hundred foreskins to Saul, he only mentions one hundred, as this was the original condition agreed upon [רד״ק, מצודת דוד].
A significant complication in reclaiming Michal is the fact that she had been given to another man in the interim. Returning to a first husband after being with a second is generally forbidden. However, the prophets of the time testified that her second husband never actually consummated the relationship. While David already knew this truth through Divine inspiration, a person is not legally trusted to testify on their own behalf. Therefore, the formal, external testimony of the prophets was necessary to legally permit Michal to return to David [חומת אנך].