"Not that we are sufficient in ourselves to claim anything as coming from us, but our sufficiency is from God..." - 2 Corinthians 3:5
When it comes to the knowledge of how one may stand before God and attain eternal life, that is truly not to be achieved by our work or power, nor to originate in our brain. In other things, those pertaining to this temporal life, you may glory in what you know, you may advance the teachings of reason, you may invent ideas of your own; for example: how to make shoes or clothes, how to govern a household, how to manage a herd. In such things exercise your mind to the best of your ability. Cloth or leather of this sort will permit itself to be stretched and cut according to the good pleasure of the tailor or shoemaker. But in spiritual matters, human reasoning certainly is not in order; other intelligence, other skill and power, are requisite here – something to be granted by God himself and revealed through his Word.
What mortal has ever discovered or fathomed the truth that the three persons in the eternal divine essence are one God; that the second person, the Son of God, was obliged to become man, born of a virgin; and that no way of life could be opened for us, save through his crucifixion? Such truth never would have been heard nor preached, would never in all eternity have been published, learned and believed, had not God himself revealed it.
For this season they are blind fools of first magnitude and dangerous characters who would boast of their grand performances, and think that the people are served when they preach their own fancies and inventions. It has been the practice in the Church for anyone to introduce any teaching he saw fit; for example, the monks and priests have daily produced new saints, pilgrimages, special prayers, works and sacrifices in the effort to blot out sin, redeem souls from purgatory, and so on. They who make up things of this kind are not such as put their trust in God through Christ, but rather such as defy God and Christ. Into the hearts of men, where Christ alone should be, they shove the filth and write the lies of the devil. Yet they think themselves, and themselves only, qualified for all essential teaching and work, self-grown doctors that they are, saints all-powerful without the help of God and Christ.
“But our sufficiency is from God.”
Of ourselves – in our own wisdom and strength – we cannot effect, discover nor teach any counsel or help for man, whether for ourselves or others. Any good work we perform among you; any doctrine we write upon your heart – that is God’s own work. He puts into our heart and mouth what we should say, and impresses it upon your heart through the Holy Spirit. Therefore, we cannot ascribe to ourselves any honor therein, cannot seek our own glory as the self-instructed and proud spirits do; we must give to God alone the honor, and must glory in the fact that by his grace and power he works in you unto salvation.
In short, let him who would be wise, who would boast of great skill, talents and power, confine himself to things other than spiritual; with respect to spiritual matters, let him keep his place and refrain from boasting and pretense. For it is of no moment that men observe your greatness and ability; the important thing is that poor souls may rest assured of being presented with God’s Word and works, whereby they may be saved.
(This is an excerpt from a longer sermon preached by Martin Luther)