The passuk in Vayikra 6:0 states “Eat matzah in a holy place.”

What is that holy place?

The Tiferes Shlomo answers that it is the mouth. 

One should make his mouth a holy place, fitting to eat the matzah. We do so by undertaking to refrain from speaking lashon hara and other forms of forbidden speech, and by not consuming non-kosher foods.