It is narrated from Hazrat Buraidah (may Allah be pleased with him) that I heard the Noble Prophet (peace and blessings be upon him) say: "Make this black seed obligatory upon yourselves, for there is healing in it."
Hadith Referenceمسند احمد / مسند الأنصار رضي الله عنهم / 22999
Hadith Gradingحکم دارالسلام:صحيح لغيره ، وهذا إسناد قوي