The following quotes come from, what Luther saw as his most important work,"The Bondage of the Will". "De Servo Arbitrio" is the classic statement of the religion of faith. It is solidly rooted in Scripture. If Luther is correct in his thesis, then all religions predicated on human ability are woefully mistaken.
For context, Luther, is responding to some of Erasmus' assertions in support of man's natural moral ability to obey the gospel. Erasmus presupposed that all of God's commands to obey proved that we had the "free-will" or moral ability to do so. Erasmus would often ask, "if we can do nothing, what is the purpose of all the laws, precepts, threats and promises in the Bible? All these precepts are useless if nothing is attributed to the human will. If it is not in the power of every man to keep what is commanded, all the exhortations of Scripture are of necessity useless," In response, Luther, with great wit and irony exposes why Erasmus position on free will is an erroneous, unscriptural doctrine which, ultimately, undermines the gospel itself.