Musnad Ahmed: Hadith 3795

The Messenger of Allah (ﷺ) said: “Beware of sins that are thought of as little, because they accumulate until they cause a man's doom.” The Messenger of Allah (ﷺ) gave us the likeness of that: the likeness of people who have halted in the desert and the time comes to cook, so one man goes out and brings a stick, and another man brings another stick, until they have accumulated a lot, then they light a fire and cook what they put on it.”