Ibn Ammar said that he heard Sawwar ibn Shabib al-A’raji say that he was sitting in Abdullah ibn `Umar’s house when a man came and said: “O Ibn ‘Umar! There are groups of people bearing witness against us and attributing to us disbelief [Kufr] and associating partners with Allah [Shirk].”
Ibn `Umar replied: “What is wrong with you! Why didn’t you just say: ‘La ilaha Illa Allah’?!”
When he said this the entire household began to say La ilaha Illa Allah until the house was shaking.”
(Related by Imam Ibn ‘Asakir in Tibyan al-Kadhib al-Muftari, Pg. 373 – The Fitna of Takfir)
May Allah be pleased with them.