The Imitation of Christ, by Thomas a Kempis, tr. by William Benham [1886], at sacred-texts.com
"My Son, for this thou must diligently make thy endeavour, that in every place and outward action or occupation thou mayest be free within, and have power over thyself; and that all things be under thee, not thou under them; that thou be master and ruler of thy actions, not a slave or hireling, but rather a free and true Hebrew, entering into the lot and the liberty of the children of God, who stand above the present and look upon the eternal, who with the left eye behold things transitory, and with the right things heavenly; whom temporal things draw not to cleave unto, but who rather draw temporal things to do them good service, even as they were ordained of God to do, and appointed by the Master Workman, who hath left nought in His creation without aim and end.
2. "And if in any chance of life thou stand not in outward appearances, nor judgest things which are seen and heard by the fleshly sense, but straightway in every cause enterest with Moses into the tabernacle to ask counsel of God; thou shalt hear a divine response and come forth instructed concerning many things that are and shall be. For always Moses had recourse to the tabernacle for the solving of all doubts and questionings; and fled to the help of prayer to be delivered from the dangers and evil deeds of men. Thus also oughtest thou to fly to the secret chamber of thy heart, and earnestly implore the divine succour. For this cause we read that Joshua and the children of Israel were deceived by the Gibeonites, that they asked not counsel at the mouth of the Lord,(1) but being too ready to listen to fair speeches, were deceived by pretended piety."
(1) Joshua ix. 14.