Qur'an, Al-Furqan, Surah 25:63-68a
The true servants of the merciful Lord are those who walk on the earth in humility; who, when they are accosted by ignorant people, wish them peace; and who spend the night standing and kneeling, in adoration of God. The true servants of the merciful Lord are those who are neither extravagant nor stingy, but keep the mean between these two extremes; who invoke no god apart from God.