John Gill's Bible Commentary Ver. 5. Not that we are sufficient of ourselves , etc..] 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.
Matthew Henry Commentary
Verses 1-11 - Even the appearance of self-praise and courting human applause, is painful to the humble and spiritual mind. Nothing is more delightful to faithful ministers, or more to their praise, than the success of their ministry, as shown in the spirits and lives of those among whom the labour. The law of Christ was written in their hearts, and the love of Christ shed abroad there. Nor was it written in tables of stone, as the law of God given to Moses, but on the fleshy (not fleshly, a fleshliness denotes sensuality) tables of the heart, Eze 36:26. Their hearts were humbled and softened to receive this impression, by the new-creating power of the Holy Spirit. He ascribes all the glory to God. And remember, as our whole dependence is upon the Lord, so the whole glory belongs to him alone. The letter killeth: the letter of the law is the ministration of death; and if we rest only in the letter of the gospel, we shall not be the better for so doing: but the Holy Spirit gives life spiritual, and life eternal. The Old Testamen dispensation was the ministration of death, but the New Testament of life. The law made known sin, and the wrath and curse of God; it showe us a God above us, and a God against us; but the gospel makes know grace, and Emmanuel, God with us. Therein the righteousness of God by faith is revealed; and this shows us that the just shall live by his faith; this makes known the grace and mercy of God through Jesu Christ, for obtaining the forgiveness of sins and eternal life. The gospel so much exceeds the law in glory, that it eclipses the glory of the legal dispensation. But even the New Testament will be a killin letter, if shown as a mere system or form, and without dependence of God the Holy Spirit, to give it a quickening power.
Greek Textus Receptus
ουχ 3756 PRT-N οτι 3754 CONJ ικανοι 2425 A-NPM εσμεν 2070 5748 V-PXI-1P αφ 575 PREP εαυτων 1438 F-3GPM λογισασθαι 3049 5664 V-ADN τι 5100 X-ASN ως 5613 ADV εξ 1537 PREP εαυτων 1438 F-3GPM αλλ 235 CONJ η 3588 T-NSF ικανοτης 2426 N-NSF ημων 2257 P-1GP εκ 1537 PREP του 3588 T-GSM θεου 2316 N-GSM
Robertson's NT Word Studies
3:5 {Of ourselves} (af' heautwn). Starting from ourselves (reflexive pronoun). {As from ourselves} (hws ex hautwn). He says it over again with preposition ex (out of). He has no originating power for such confidence. {Sufficiency} (hikanotes). Old word, only here in N.T.