Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) reports this saying of the Prophet (peace and blessings be upon him): "If people knew the virtue of calling the adhan, they would take up swords against one another for it."
Ahmad recorded it; its chain contains a narrator, Ibn Lahi'ah, and there is weakness in him.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 1827