Disbelief according to the Murji'ah, and that it is specific to them as mere denial by the heart only.

Khalid al-Anbari: The faith intended in this hadith is valid faith, even if it is only a mustard seed. If faith—or rather, if belief—encounters hatred of Allah and arrogance toward the commands of Allah (Exalted and Majestic is He), then this arrogance undoubtedly contradicts this faith and erases it from the heart. Therefore, the Murji'ah confined disbelief to denial by the heart, and they assumed, as the Shaykh al-Islam says, that anyone whom the Lawgiver declared a disbeliever was declared so only because of the absence of belief in the heart regarding the Lord (Blessed and Exalted is He). It is well known that there is no way to know or uncover denial by the heart. Consequently, as "Ibn al-Wazir" says, a person's disbelief is never established except by a specific text regarding that particular individual. The Salaf declared disbelievers those who hold this view. Iblis the accursed is a disbeliever by the text of the Qur'an, and he was not a denier; rather, he was a stubborn enemy of Allah, arrogant. Iblis undoubtedly had belief in his heart, and yet he disbelieved by the text of the Noble Book. Likewise, Pharaoh and his people, as our Lord said: , and He also said: . The harm they caused to the people of Moses, even though they knew by the text of the Noble Book that he was a messenger of Allah; this harm, and what results from it, which is a lack of respect for the Messenger and a lack of loyalty to him, undoubtedly contradicts this belief. Therefore, our Lord (Blessed and Exalted is He) declared them disbelievers, as ... says.