It is narrated from Hazrat Abu Musa (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: "There is no marriage without a guardian (wali)."
Hadith Referenceمسند احمد / تتمہ مُسْنَدِ الْكُوفِيِّينَ / 19746
Hadith Gradingحکم دارالسلام:حديث صحيح، وهذا إسناد محفوظ