Jami` at-Tirmidhi 3189

Narrated Mus'ab bin Sa'd:that his father, Sa'd, said: "Four Ayat were revealed about me" and he mentioned the story. Umm Sa'd had said: "Did not Allah command you to honor (your parents). By Allah! I will not eat or drink anything until I die or you renounce (Islam)." He said: "So when they wanted to make her eat, they would force her mouth open. So this Ayah was revealed: And We have enjoined on man to be dutiful to his parents; but if they strive to make you associate (partners) with Me, of which you have no knowledge, then obey them not (29:)