The text of today begins immediately after Jesus has spoken the woes against the Pharisees and scribes. Though there is a large crowd, which has gathered, Jesus speaks first to his disciples cautioning them against the yeast of the Pharisees.
The yeast of the Pharisees is identified as hypocrisy only in the Gospel of Luke. To be a hypocrite (Greek hupokrisis) originally meant to wear a mask or to play a role. The point that is being made is that at the judgment, everyone’s true character will be revealed. There will be no masks, and everyone will be seen as he or she is. Even the sparrow which is so insignificant when compared to human beings is looked after by God therefore, there is no need to be afraid, because a God who is and will always remain, Father, will judge us.
Though Jesus constantly revealed God as unconditional love, many of us still relate to him from fear. This is the reason why we wear masks before him and consequently before others. We are afraid to be ourselves. If we begin to realise that our God is a God who primarily wants to save, we can improve our relationship with him and with others.