Faith increases with obedience and decreases with sins.

Question:
The stronger position is that faith increases with acts of obedience and decreases with sins. What is the evidence for this? Is it so?

Answer:
Answer: Faith is a statement of the tongue, a belief of the heart, and an action of the limbs. It increases with obedience and decreases with sins. The evidence for its increase is the saying of Allah (Glorified and Exalted is He): “Indeed, the believers are only those who, when Allah is mentioned, their hearts become fearful, and when His verses are recited to them, it increases them in faith, and in their Lord they place their trust. Those who establish prayer and spend from what We have provided them. Those are the true believers.” It increased them in faith. Some say: “Who among you has had his faith increased by this? As for those who believed, it increased them in faith, and they rejoice.” This indicates that faith increases with obedience and decreases with sin. The evidence for this is the saying of the Prophet (peace and blessings be upon him): “Whoever among you sees an evil, let him change it with his hand; if he cannot, then with his tongue; if he cannot, then with his heart, and that is the weakest of faith.” In another narration: “There is not a mustard seed’s weight of faith behind that.” And in his saying in the hadith that Allah (Exalted and Majestic is He) says to the angels: “Allah the Exalted says: Take out of the Fire whoever has in his heart the weight of a mustard seed of faith.” Less than the weight of a mustard seed of faith.