Hawzah News Agency – The merciful prophet of Islam, peace be upon him and his household says:

الإيمانُ مَعرِفةٌ بالقلبِ، وقَولٌ باللِّسانِ، وعَملٌ بالأرْكانِ.

'Faith is inner knowledge by means of the heart, attestation with the tongue and action with the limbs.'

Source: Kanz al-Ummal, no. 2