And the LORD said to Satan, “Have you considered my servant Job, that there is none like him on the earth, a blameless and upright man, who fears God and turns away from evil? He still holds fast his integrity, although you incited me against him to destroy him without reason.” — Job 2:3

An upright heart is first a perfect [or complete: teleios] heart, as the Scripture terms it. It is an entirely whole heart, which is when all the powers go one and the same way, when the whole soul is bent after God and is driven only to seek and honor Him.

You may best know it by the contrary; the hypocrite’s heart is a divided heart. He looks two ways at once, as one power and faculty of the soul is against another. There is (‘tis true) a fight within the best people, but then it is between grace and flesh, between a man and his enemy. But in the hypocrite, one faculty takes part against the other. Here is reason and conscience against affection, and one affection against another.

There is a wise difference between civil war, where one neighbor is against another, and a national war, where they all join together against a common enemy. The Christian man’s fight is of the whole regenerated part against corruption; but in the hypocrite’s heart there is civil war. The powers are altogether at odds with themselves, as if one member in the body should fight against another. Passion commends a thing, reason condemns it; lust affects a thing, conscience refuses it; one part would have one thing, and another part another.

In the upright man it is far otherwise; his heart is entire, and goes all one way; he desires in all things to please God and fight against sin.

—Robert Harris
Member of the Westminster Assembly
President of Trinity College, Oxford
A.D. 1581-1658