Since the physical body of the Buddha no longer exists after his extinction, the direct object of our worship should then become his teachings, whose substance is preserved in the form of the Sutra or a scroll of the Sutra. The Sutra is the spirit of the Buddha, or another form of his manifestation. If we focus on the time after the Buddha’s extinction, the Sutra or a scroll of the Sutra replaces his physical manifestation. In this sense, respecting and making offerings to the Sutra or a scroll of the Sutra is exactly the same as respecting and making offerings to the Buddha himself. Indeed, when we believe, worship, and make offerings to the Lotus Sutra, we in fact believe, worship, and make offerings to the living Buddha. Furthermore, through these practices, we are considered to be worshiping the Original Buddha of Eternal Existence. [Chapter 10: The Teacher of the Dharma] and those which follow will gradually clarify what we mean by this.
Introduction to the Lotus Sutra