'Sincere' in the Bible

so that you may approve the things that are excellent, in order to be sincere and blameless until the day of Christ;

But the goal of our instruction is love from a pure heart and a good conscience and a sincere faith.

For I am mindful of the sincere faith within you, which first dwelt in your grandmother Lois and your mother Eunice, and I am sure that it is in you as well.

let us draw near with a sincere heart in full assurance of faith, having our hearts sprinkled clean from an evil conscience and our bodies washed with pure water.

Since you have in obedience to the truth purified your souls for a sincere love of the brethren, fervently love one another from the heart,

This is now, beloved, the second letter I am writing to you in which I am stirring up your sincere mind by way of reminder,