2 cor 3:5

Not that we are sufficient of ourselves - We do not arrogate to ourselves any power to enlighten the mind or change the heart, we are only instruments in the hand of God. Nor was it possible for us apostles to think, to invent, such a scheme of salvation as is the Gospel; and if we even had been equal to the invention, how could we have fulfilled such promises as this scheme of salvation abounds with? God alone could fulfill these promises, and he fulfils only those which he makes himself. All these promises have been amen-ratified and fulfilled to you who have believed on Christ Jesus according to our preaching; therefore, ye are God's workmanship and it is only by God's sufficiency that we have been able to do any thing. This I believe to be the apostle's meaning in this place, and that he speaks here merely of the Gospel scheme, and the inability of human wisdom to invent it; and the words λογισασθαι τι, which we translate to think any thing, signify, properly, to find any thing out by reasoning; and as the Gospel scheme of salvation is the subject in hand, to that subject the words are to be referred and limited. The words, however, contain also a general truth; we can neither think, act, nor be, without God. From him we have received all our powers, whether of body or of mind, and without him we can do nothing. But we may abuse both our power of thinking and acting; for the power to think, and the power to act, are widely different from the act of thinking, and the act of doing. God gives us the power or capacity to think and act, but he neither thinks nor acts for us. It is on this ground that we may abuse our powers, and think evil, and act wickedly; and it is on this ground that we are accountable for our thoughts, words, and deeds.

Not that we are sufficient of ourselves,.... Though we are sufficient for this work to which God has called us, and have such trust and confidence that he has blessed and owned us, and done such great things by us; yet we do not ascribe anything to ourselves, to any power of ours, to any self-sufficiency in us: for "we are not sufficient of ourselves" neither for the work of the ministry, nor for the conversion of sinners, nor for faith and hope in God, nor for any spiritual work whatever; not even to think anything as of ourselves; any good thing, either for our own use and benefit, or for the advantage of others; we are not able of ourselves to meditate with judgment and affection upon the word of God, to study the Scriptures, to collect from them things fit for the ministry; and much less with freedom and boldness to speak of them to edification; and still less able to impress them upon the heart: for though you who are the epistle of Christ are ministered by us, yet not by any power and self-sufficiency of ours; but our sufficiency is of God; to think, to speak, and to act for his glory.