It is narrated from Sayyiduna Anas (may Allah be pleased with him) that once I was sitting with Sayyiduna Ubayy bin Ka'b and Sayyiduna Abu Talhah. We ate bread and meat, then I asked for water to perform ablution. Both of them said, "Why are you performing ablution?" I said, "Because of the food we have just eaten." They said, "Will you perform ablution because of lawful things? That person, who was better than you, did not perform ablution because of this."