“A. For the right understanding of the ten commandments, these rules are to be observed:
. . .
6. That under one sin or duty, all of the same kind are forbidden or commanded; together with all the causes, means, occasions, and appearances thereof, and provocations thereunto (Matt. 5:21-22, 27-28; Matt. 15:4-6; Heb. 10:24-25; 1 Thess. 5:22; Jude 1:23; Gal. 5:26; Col. 3:21).” (WLC 99).

Thomas Watson
The Beatitudes: An Exposition of Matthew 5:1-12

4. A pure heart avoids the appearance of evil. “Abstain from all show of evil” (1 Thessalonians 5:22). A pure heart avoids that which may be interpreted as evil. He that is loyal to his prince not only forbears to have his hand in treason, but he takes heed of that which has a show of treason. A gracious heart is shy of that which looks like sin. When Joseph’s mistress took hold of him and said, “Lie with me,” he left his garment in her hand and fled from her (Genesis 39:12). He avoided the appearance of evil. He would not be seen in her company. Thus a pure heart avoids whatever may have the suspicion of sin:

(i) In regard of himself, and that two ways. First, because the appearance of evil is oftentimes an occasion of evil. Effeminate dalliance is an appearance of evil, and many times occasions evil. Had Joseph been familiar with his mistress in a wanton sporting manner, he might in time have been drawn to commit folly with her. Some out of novelty and curiosity have gone to hear mass, and afterwards have lent the idol not only their ear but their knee. In our times are there not many who have gone with itching ears into sectarian company and have come home with the plague in their head? When Dinah would be gadding, she lost her chastity (Genesis 34:2). A pure heart foreseeing the danger avoids the appearance of evil. It is dangerous to go near a hornets’ nest. The men who went near the furnace were burned (Daniel 3:22). Second, because the appearance of evil may eclipse his good name. A good name is a precious ointment. It is better than fine gold (Proverbs 22:1). It commends us to God and angels, which riches cannot do. Now a godly man avoids the appearance of evil, lest he wound his good name. What comfort can there be of life, when the name lies buried?

(ii) A pure heart avoids the suspicion of sin out of reverence and respect to the holiness of God. God hates the very appearance of evil. God abhors hypocrites because they have no more than the appearance of good, and he is angry with his children if they have so much as the appearance of evil. A gracious heart knows God is a jealous God and cannot endure that his people should border upon sin. Therefore he keeps aloof off and will not come near the smell of infection.

(iii) A pure heart avoids the show of sin in regard of the godly. The appearance of evil may scandalize a weak brother. A gracious heart is not only fearful lest he should defile his own conscience, but lest he should offend his brother’s conscience. Were it only a thing indifferent, yet if it be an appearance of evil and may grieve another, we are to forbear (1 Corinthians 10:25-28). For when we sin against the brethren and wound their weak conscience, we sin against Christ (1 Corinthians 8:12). The weak Christian is a member of Christ. Therefore the sinning against a member is a sinning against Christ.

(iv) A pure heart avoids the very appearance of evil in regard of the wicked. The apostle would have us walk wisely towards them that are without (1 Thessalonians 4:12). The wicked watch for our halting. How glad would they be of anything to reproach religion? Professors are placed as stars in the highest orb of the church, and if there be but the appearance of any eccentric, or irregular motion, the wicked would presently open their mouths with a fresh cry against religion. Now to a godly heart the fame and honour of the gospel is so dear that he had rather die than impeach or eclipse it. By this then let us try ourselves whether we are pure in heart. Do we avoid the least apparition of sin? Alas, how many run themselves into the occasions of sin! They tempt the devil to tempt them. Some go to masques and comedies, the very fuel and temptation to lust. Others frequent erroneous meetings, and truly God often in just judgment leaves them to the acts of sin, that do not avoid the appearance of sin. “They were mingled among the heathen and learned their works” (Psalm 106:35). Pure hearts fly the occasion. John would not endure the company of Cerinthus in the bath, as Nicephorus notes. Polycarp would have no conference with Marcion the heretic, but called him the devil’s firstborn. Basil says that the Christians in his time avoided the meetings of sectaries as the very schools of error. Oh, avoid the appearance of evil. The apostle bids us to follow those things which are of good report (Philippians 4:8).