Tau is the last letter of the Hebrew alphabet and is believed to be the symbol with which Ezekiel marked those chosen by God? This reference is found in the Book of Ezekiel 9:4. The symbolism of Tau has played a crucial role in Christian theology and has been associated with divine selection and protection.

Furthermore, it is worth noting that Pope Innocent I|l made a profound gesture during the opening of the Fourth Lateran Council in 1215. He delivered a homily focusing on the Scripture passage related to the Tau symbol. This event was of particular importance to St Francis, underscoring the enduring relevance of Tau in shaping Christian beliefs and practices throughout history.