The beatitudes

Well, if the heart be thus deceitful, what need have we with all keeping to keep the heart! do with the heart, as with a cheater; we will trust a cheater no further than we can see him; the heart is a grand cheater, it will supplant and cozen; try it, but do not trust it. Prov. 28.26. He that trusteth in his own heart is a fool.

2. We must excubias agere, keep the heart with watch and ward, because it is not only false, but fickle. God complains of Israel, that their goodness was as the early dew, Hos. 6.4. The Sun ariseth, and the dew vanisheth; ⟨p. 541⟩the heart sometimes seems to be in a good frame, but it soon alters; set the water on the fire, it boils; set it in the open Air, it freezeth: Those good affections which boil in the Church, often freeze in the Shop; one day a Christian is quick and lively in prayer, another day like the Disciples, heavy and sleeping, Luke 22.45. At one time a Christian is like David, when he danced before the Ark with all his might, 2 Sam. 6.14: At another time like Sampson, when his hair was shaved, and his strength went from him, Judges 16.19. When the gold hath been made pure in the fire, it remains pure; but it is not so with the heart; when it hath been purified in an Ordinance, it doth not remain pure, it gathers new soil and dross. The heart is one day humble, next day proud; one one day meek, the next day passionate; one day quick in its motion towards heaven, the next day the clock is set back; 'tis with the heart, as with a sick mans pulse, which alters almost every quarter of an hour. The heart being so full of variation and inconstancy, it is needful to keep the heart with all keeping; the heart like a Viol, will soon be out of order, therefore we must often screw up the strings, and keep the instrument in tune, that we may make melody in our heart to the Lord