Sayyiduna Ali (may Allah be pleased with him) said: When this verse was revealed to the Messenger of Allah (peace and blessings be upon him): "And warn your nearest kinsfolk, and lower your wing to those of the believers who follow you" [Surah al-Shu'ara: 214-215], the Messenger of Allah (peace and blessings be upon him) said: "I knew that if I began with my people with it, I would see from them what I dislike, so I kept silent about conveying it. Then Jibril (peace be upon him) came to me and said: O Muhammad! If you do not fulfil this command of your Lord, He will punish you." Then he (peace and blessings be upon him) related the story of gathering them and warning them.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 17726