All true Christians are good and faithful soldiers of Jesus Christ, and “fight the good fight of faith;” for none but those who do so, “ever lay hold on eternal life.” Those who “fight as those who beat the air,” never win the crown of victory. “They that run in a race, run all, but one wins the prize,” and they that are slack and negligent in their course do not “so run as that they may obtain.” The kingdom of heaven is not to be taken but by violence. Without earnestness there is no getting along in that narrow way that leads to life; and so no arriving at that state of glorious life and happiness which it leads to. Without earnest labour there is no ascending the steep and high hill of Zion, and so no arriving at the heavenly city on the top of it. Without a constant laboriousness there is no stemming the swift stream in which we swim, so as ever to come to that fountain of water of life that is at the head of it. There is need that we should “watch and pray always, in order to our escaping those dreadful things that are coming on the ungodly, and our being counted worthy to stand before the Son of man.” There is need of our “putting on the whole armour of God, and doing all, to stand,” in order to our avoiding a total overthrown, and being utterly destroyed by “the fiery darts of the devil.” There is need that we should “forget the things that are behind, and be reaching forth to the things that are before, and pressing towards the mark for the prize of the high caling of God in Christ Jesus,” in order to our obtaining that prize. Slothfulness in the service of God in His professed servants is as damning as open rebellion; for the slothful servant is a wicked servant, and shall be cast into outer darkness among God’s open enemies (Matt. XXV. 26, 30).
Jonathan Edwards, The Religious Affections, pg. 311