“Progress of his Version. Luther was gradually prepared for this work. He found for the first time a complete copy of the Latin Bible in the University Library at Erfurt, to his great delight, and made it his chief study. He derived from it his theology and spiritual nourishment; he lectured and preached on it as professor at Wittenberg day after day. He acquired the knowledge of the original languages for the purpose of its better understanding. He liked to call himself a "Doctor of the Sacred Scriptures."
He made his first attempt as translator with the seven Penitential Psalms, which he published in March, 1517, six months before the outbreak of the Reformation. Then followed several other sections of the Old and New Testaments,—the Ten Commandments, the Lord's Prayer, the Prayer of King Manasseh, the Magnificat of the Virgin Mary, etc., with popular comments. He was urged by his friends, especially by Melanchthon, as well as by his own sense of duty, to translate the whole Bible.
He began with the New Testament in November or December, 1521, and completed it in the following March, before he left the Wartburg. He thoroughly revised it on his return to Wittenberg, with the effectual help of Melanchthon, who was a much better Greek scholar. Sturz at Erfurt was consulted about coins and measures; Spalatin furnished from the Electoral treasury names for the precious stones of the New Jerusalem (Rev. 21). The translation was then hurried through three presses, and appeared already Sept. 21, 1522, but without his name.
In December a second edition was required, which contained many corrections and improvements.
He at once proceeded to the more difficult task of translating the Old Testament, and published it in parts as they were ready. The Pentateuch appeared in 1523; the Psalter, 1524.”

Luther's competence as a Bible translator