Blessed are the pure in heart, for they shall see God. Matt. 5:8.
The reasons for purity are:
Purity is a thing called for in Scripture: ‘Be ye holy for I am holy’. It is not only the minister bids you be holy, but God himself calls for it. What should the Holy God do with unholy servants?
Because of that filthy and cursed condition we are in before purity be wrought in us. We are a lump of clay and sin mingled together. Sin not only blinds us, but defiles us. It is called filthiness (James 1:21). And to show how befilthying a thing it is, it is compared to a plague-sore (1 Kings 8:38), to spots (Deuteronomy 32:5), to a vomit (2 Peter 2:22), and to a ‘menstruous cloth’ (Isaiah 30:22), which (as Jerome says) was the most defiling thing under the law. All the legal warnings which God appointed were but to put men in mind of their loathsomeness before they were washed in the blood of Christ. If all the evils in the world were put together and their quintessence strained out, they could not make a thing so black and polluted as sin does. A sinner is a devil in man’s shape. When Moses’ rod was turned into a serpent, he fled from it. Would God open men’s eyes and show them their deformities and damnable
spots, they would be afraid and fly from themselves as serpents! This shows what need we have of purity. When grace comes it washes off this hellish filth. It makes them who are as black as hell to become white as snow.
Because none but the pure in heart are interested in the covenant of grace. Covenanted persons have ‘the sprinkling with clean water’ (Ezekiel 36:25). Now, till we are thus sprinkled, we have nothing to do with the new covenant and by consequence with the new Jerusalem.
Purity is the end of our election. ‘He has chosen us that we should be holy’ (Ephesians 1:4). Not for holiness, but to holiness. ‘Whom he did foreknow, he also did predestinate to be conformed to the image of his Son’ (Romans 8:29). God predestinates us to Christ’s image, which image consists ‘in righteousness and true holiness’ (Ephesians 4:24). So that till you are holy, you cannot show any sign of election upon you, but rather the devil’s brand-mark.
Purity is the end of our redemption. If we could have gone to heaven in our sins, Christ needed not have died. Why did he shed his blood but to redeem us from ‘a vain conversation’? (1 Peter:18, 19); and, ‘who gave himself for us that he might redeem us from all iniquity, and purify unto himself a peculiar people’ (Titus 2:14). Christ shed his blood to wash off our filth. The cross was both an altar and a laver. Jesus died not only to save us from wrath, but to save us from sin (Matthew 1:21). Out of his side came water which signifies our cleansing, as well as blood which signifies our justifying (1 John 5:6). The truth is, it were to make the body of Christ monstrous, if the head should be pure and not the members. Thomas Watson