'Heart' in the Bible

to Timothy, my beloved son: Grace, mercy, and peace [inner calm and spiritual well-being] from God the Father and Christ Jesus our Lord.

I give praise to God, whose servant I have been, with a heart free from sin, from the time of my fathers, because in my prayers at all times the thought of you is with me, night and day

I remember your sincere and unqualified faith [the surrendering of your entire self to God in Christ with confident trust in His power, wisdom and goodness, a faith] which first lived in [the heart of] your grandmother Lois and your mother Eunice, and I am confident that it is in you as well.

Flee also youthful lusts: but follow righteousness, faith, charity, peace, with them that call on the Lord out of a pure heart.

Gently guiding those who go against the teaching; if by chance God may give them a change of heart and true knowledge,