Sin rarely stops at one act; people soon add another and another to the chain. James 1:12-16 lists the steps leading to sin, beginning with temptation, and Jeremiah 9:3 describes the course: "they proceed from evil to evil, and they do not know Me." This is a major reason God uses leaven to symbolize sin. As leaven spreads through a lump of dough, sin spreads and corrupts the lives of all it touches. The sequence that begins in Genesis 37 illustrates this. Jacob's favoritism toward Joseph irritated his brothers, their irritation grew into jealousy and flared into hatred, and they conspired to murder, sold Joseph into slavery, and deceived their father to hide their guilt. One sin bred others, damaged their relationship with Jacob, and intensified his over-protectiveness of Benjamin, which made things worse for them. The same process occurs in anyone's life. It also fits sin's addictive nature: each sin makes the next easier, and sin's deceitful promises keep luring people on. Sin produces more sin unless someone stops it by repenting.

Sin is addictive and self-propagating. Like a drug, it demands more because what formerly satisfied no longer will, and each sin makes the next one easier because the ideal is gradually lowered and the conscience adjusts downward. A person first regards sin with horror, then feels uneasy about it, and if he continues, does it without a qualm. Repetition hardens the heart like a callus (Hebrews 3:13), making the mind insensitive, unteachable, and eventually unable to repent. A thought or act becomes a habit, and a habit becomes a necessity, so that the sinner keeps sinning because he cannot help it. Sin promises pleasure and fulfillment but never delivers enough, forcing the sinner into greater perversions until it kills him. Jesus says whoever commits sin is a slave of sin (John 8:34), so the sinner is doing what sin wants, not what he likes. Jeremiah describes a people who proceed from evil to evil (Jeremiah 9:3) in an unbroken chain. Jacob's favoritism toward Joseph led to the brothers' jealousy, hatred, conspiracy to murder, selling Joseph into slavery, and lying to their father. One sin can lead directly to others and affect people uninvolved in the original sin. James 1:13-16 traces the course: desire conceives and gives birth to sin, and full-grown sin brings forth death. Therefore sin must be feared and hated as an enemy, and mastered, as God told Cain, rather than allowed to rule.

Sin is a living, malignant power that is dynamic rather than static, and it actively works to reproduce itself. Each sin makes the next one easier. The first time a person sins with knowledge, he regards it with horror, but if he continues, he eventually does it without a qualm, because the ideal is gradually lowered and conscience stops operating at its former level. Sin has an addictive, drug-like quality. It promises pleasure, contentment, and fulfillment, but delivers only fleeting satisfaction, so what once satisfied no longer will, and the person is driven to greater and greater perversions. Sin deludes a person into thinking he can take it or leave it, and it offers rationalizations and a plausible, even virtuous, appearance. Over time it destroys innocence, ideals, and the will, until a habit becomes a necessity and the sinner is sin's slave. Hebrews 3:13 shows that the deceitfulness of sin hardens the heart, producing an insensitive conscience and eventually making repentance impossible. Cain was warned that sin lies at the door and desires to rule him; if he nurtured it, he would become a pro at sinning, and "the way of Cain" became a biblical proverb. Joseph's brothers illustrate the chain: a father's favoritism bred jealousy, then hatred, then a conspiracy to murder, then selling Joseph into slavery, and then lying to their father to cover the guilt. Like leaven, sin keeps touching other parts of the body and corrupting as it goes.