The resurrection of Jesus (Act_17:31) is the “assurance” (Gr. pistis, generally rendered “faith”) or pledge God has given that his revelation is true and worthy of acceptance. The “full assurance [Gr. plerophoria, ‘full bearing’] of faith” (Heb_10:22) is a fulness of faith in God which leaves no room for doubt. The “full assurance of understanding” (Col_2:2) is an entire unwavering conviction of the truth of the declarations of Scripture, a joyful steadfastness on the part of any one of conviction that he has grasped the very truth. The “full assurance of hope” (Heb_6:11) is a sure and well-grounded expectation of eternal glory (2Ti_4:7, 2Ti_4:8). This assurance of hope is the assurance of a man’s own particular salvation.
This infallible assurance, which believers may attain unto as to their own personal salvation, is founded on the truth of the promises (Heb_6:18), on the inward evidence of Christian graces, and on the testimony of the Spirit of adoption (Rom_8:16). That such a certainty may be attained appears from the testimony of Scripture (Rom_8:16; 1Jo_2:3; 1Jo_3:14), from the command to seek after it (Heb_6:11; 2Pe_1:10), and from the fact that it has been attained (2Ti_1:12; 2Ti_4:7, 2Ti_4:8; 1Jo_2:3; 1Jo_4:16).
This full assurance is not of the essence of saving faith. It is the result of faith, and posterior to it in the order of nature, and so frequently also in the order of time. True believers may be destitute of it. Trust itself is something different from the evidence that we do trust. Believers, moreover, are exhorted to go on to something beyond what they at present have when they are exhorted to seek the grace of full assurance (Heb_10:22; 2Pe_1:5-10). The attainment of this grace is a duty, and is to be diligently sought.
“Genuine assurance naturally leads to a legitimate and abiding peace and joy, and to love and thankfulness to God; and these from the very laws of our being to greater buoyancy, strength, and cheerfulness in the practice of obedience in every department of duty.”
This assurance may in various ways be shaken, diminished, and intermitted, but the principle out of which it springs can never be lost.