Summary of Sunni concepts
Achieving monotheism produces a sound heart
Anyone who has achieved the monotheism of God in his divinity, lordship, names, and attributes is undoubtedly the owner of a sound heart
Whoever achieves the unity of divinity, sincerity in worship, love, fear, etc., is achieved in him
And whoever achieves the oneness of divinity in him, trust in God, certainty in His promise, hope, and refuge in Him, Glory be to Him, etc., is achieved in him.
Whoever achieves the unification of names and attributes will know the Most Beautiful Names of God and His Most High Attributes with complete knowledge
It affected his heart and resulted in the heart work appropriate to each of His attributes, Glory be to Him
So he repents to God Almighty, exposing himself to the attributes of pardon, mercy, and forgiveness, and he trusts in God, exposing himself to the attributes of the Provider, the Giver, the Most Gracious, and so on.
This is why many predecessors interpreted a sound heart as a heart free from polytheism
Summary of Sunni concepts