When plague struck in 1603 he retreated to Chiswick to teach the boys of the Westminster school, where he preached a plague sermon on 21 August arguing in favour of leaving London under such circumstances. His argumentation rested on the Old Testament's commands to avoid exposing oneself to contagion, to avoid contact with lepers, etc. Andrewes claimed that the plague was caused by "inventions" like "new meats in diet" and "new fashions in apparel" that had roused the wrath of God. He condemns changes in Christian tradition that "our fathers never knew of".