When I saw that some people of little virtue and of much defilement were seeking the teachings of the Lesser Vehicle, I told them, ‘I renounced my family when I was young, and attained Anuttara-samyak-saṃbodhi [forty and odd years ago].’ In reality I became the Buddha in the remotest past as I previously stated. I told them so as an expedient to teach them, to lead them into the Way to Buddhahood.

In Chapter Sixteen of the Lotus Sutra, the Buddha gives this explanation of a parable he tells in Chapter Three. In that story, the foolish children of a wise man were playing in a burning house. The man tried to warn his children of the dangers of the house, but the children were so preoccupied with their games they would not leave. Only when the man promised them better toys outside would the children leave the house. The words used by the wise man were meant to get the children out of the house, even though the toys did not exist. These words were necessary to motivate the children to set aside their delusions. They were not meant to be taken literally. We learn from this explanation how the Buddha uses words, and why we formerly needed his expedient teachings.