Hadith: There is no marriage except with a guardian

عن أبي موسى رضي الله عنه أن النبي صلى الله عليه وسلم قال:
«لا نِكَاحَ إِلّا بِوَليٍّ».
[صحيح] - [رواه أبو داود والترمذي وابن ماجه وأحمد] - [سنن أبي داود: 2085]

Abu Mūsa al-Ash‘ari (may Allah be pleased with him) reported: The Prophet (may Allah's peace and blessings be upon him) said:
"There is no marriage except with a guardian."
[Authentic] - [Narrated by Abu Dāwūd, At-Tirmidhi, Ibn Mājah, and Ahmad] - [Sunan Abi Dawood - 2085]

Explanation

The Prophet (may Allah's peace and blessings be upon him) points out that a woman's marriage is not valid without a guardian who concludes the marriage contract.

Benefits from the Hadith

1. The guardian is a prerequisite for the validity of marriage. If the marriage occurs without a guardian or a woman marries herself off, the marriage is not valid.
2. The guardian is the closest man to a woman. No distant guardian can marry her off while a closer guardian is available.
3. A guardian must be: accountable, male, wise, aware of the interests related to marriage, and have the same religion as the one under his guardianship. Whoever does not fulfill these requirements is not qualified to be a guardian in a marriage contract.