faith, Islam, and excellence”—he distinguished between the two, saying: “Faith is to believe in Allah, His angels, His Books, and His messengers,” and so on.

In the Musnad, the Prophet, peace and blessings be upon him, is reported to have said:

“Islam is outward, while faith is in the heart.”

Thus, when he mentioned them together, he explained that faith is in the heart, while Islam consists of outward deeds. When he mentioned faith alone, he included outward deeds within it, because they necessarily follow from what is in the heart. Whenever faith and assent to what the Messenger has conveyed become established in the heart, their necessary effects must inevitably follow. No one conceals anything within himself without Allah revealing it in his facial expressions and unguarded words. Once assent is established in the heart, action in accordance with it can never fail to follow. Complete knowledge and genuine love cannot be firmly established without producing an outward effect.

This is why Allah denies faith to those who lack its necessary consequences: the absence of a necessary consequence entails the absence of that which necessitates it. Thus, the Most High says:

“Had they believed in Allah, the Prophet, and what was revealed to him, they would not have taken them as allies.”

He also says:

“You will not find a people who believe in Allah and the Last Day maintaining affection for those who oppose Allah and His Messenger.”

And so the verse continues; other verses convey the same meaning. The outward and the inward are inseparably linked: outward conduct cannot be upright unless the inward state is upright, and when the inward state is upright, outward conduct must also be upright. This is why the Prophet, peace and blessings be upon him, said:

“Indeed, in the body there is a piece of flesh: if it is sound, the rest of the body is sound, and if it is corrupt, the rest of the body is corrupt. Indeed, it is the heart.”