The golden rule for understanding spiritually is not intellect, but obedience. If a man wants scientific knowledge, intellectual curiosity is his guide; but if he wants insight into what Jesus Christ teaches, he can only get it by obedience. (My Utmost for His Highest)

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Watch the things you shrug your shoulders over, and you will know why you do not go on spiritually. First go - at the risk of being thought fanatical you must obey what God tells you. (My Utmost for His Highest)

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Speak to thy soul thus, "If I were dealing with a man's promise, I should carefully consider the ability and the character of the man who had covenanted with me. So with the promise of God; my eye must not be so much fixed upon the greatness of the mercy-that may stagger me; as upon the greatness of the promiser-that will cheer me. My soul, it is God, even thy God, God that cannot lie, who speaks to thee. This word of his which thou art now considering is as true as his own existence. He is a God unchangeable. He has not altered the thing which has gone out of his mouth, nor called back one single consolatory sentence. Nor doth he lack any
power; it is the God that made the heavens and the earth who has spoken thus. Nor can he fail in wisdom as to the time when he will bestow the favours, for he knoweth when it is best to give and when better to withhold. Therefore, seeing that it is the word of a God so true, so immutable, so powerful, so wise, I will and must believe the promise." If we thus meditate upon the promises, and consider the Promiser, we shall experience their sweetness, and obtain their fulfilment. (Charles Spurgeon, Morning and Evening Devotional)