Dallin H. Oaks
"The Savior's commandments on the mental attitudes that should accompany prayer and fasting, like the Beatitudes and other teachings of this supreme sermon, establish an exquisitely difficult standard for mortals. As F. W. Farrar observed in his great work The Life of Christ (London: Cassell & Co., Ltd., 1874):
"It is easy to be a slave to the letter, and difficult to enter into the spirit; easy to obey a number of outward rules, difficult to enter intelligently and self-sacrificingly into the will of God; easy to entangle the soul in a network of petty observances, difficult to yield the obedience of an enlightened heart; easy to be haughtily exclusive, difficult to be humbly spiritual; easy to be an ascetic or a formalist, difficult to be pure, and loving, and wise, and free; easy to be a Pharisee, difficult to be a disciple; very easy to embrace a self-satisfying and sanctimonious system of rabbinical observances, very difficult to love God with all the heart, and all the might, and all the soul, and all the strength. (Page 469, quoted in Bruce R. McConkie, The Mortal Messiah [Salt Lake City: Deseret Book Co., 1980], 3:232.)" (Pure in Heart, p. 25)