[More important than all is] a diligent endeavor to have the power of the truths professed and contended for abiding upon our hearts, that we may not contend for notions, but that we have a practical acquaintance within our own souls. When the heart is cast indeed into the mould of the doctrine that the mind embraceth—when the evidence and necessity of the truth abides in us—when not the sense of the words only is in our heads, but the sense of the thing abides in our hearts—when we have communion with God in the doctrine we contend for—then shall we be garrisoned by the grace of God against all the assaults of men.
Quoted by John Piper in The Future of Justification from John Owen, Vindiciae Evangelicae; or, The Mystery of the Gospel Vindicated and Socinianism
Examined, Vol. 12, The Works of John Owen, ed. William Goold (Edinburgh: Banner of Truth,
1966), 52.