Musannaf Ibn Abi Shayba 9:1079

Al-Thaqafi narrated to us, from Ubayd Allah, from Nafi’, who said: The one in whose hand is the knot of marriage is the husband. As for His saying: "Unless they remit or he remits in whose hand is the knot of marriage," it is the woman whose husband divorces her before he has consummated the marriage with her. So, either she remits the half to her husband, or her husband remits [the rest], so he completes the dowry for her.