VATICAN CITY (CNS) -- Preaching one thing but doing another puts the authenticity and credibility of Christian witness at risk, Pope Francis said.

Reflecting Nov. 5 on the day's Gospel reading from St. Matthew, in which Jesus criticizes the scribes and Pharisees for being people who "preach but do not practice," the pope told Christians to consider "the distance between saying and doing" that exists in their lives.

"Because of our weakness, we all experience a certain distance between what we say and what we do," he told the approximately 23,000 people gathered in St. Peter's Square. But he noted that it is something else to have a "duplicitous heart" in which one lives with "one foot on both sides of the fence" without problem.

"This duplicity of heart puts the authenticity of our witness as well as our credibility as persons and as Christians at risk," the pope said, especially urging people in roles of responsibility -- whether in their lives, society or the church -- to say, "no to duplicity!"

"This rule is always valid for a priest, a pastoral worker, a politician, a teacher, or a parent: be committed to living first what you say, what you preach to others," he said. "To be authentic teachers, we first need to be credible witnesses."

Pope Francis said that because of their duplicity, the scribes and Pharisees "performed works to appear righteous" and "save face" in order to hide their inconsistencies and save their reputations. He likened such a practice to applying make-up, not only on their faces but also on their lives and hearts.

"These 'made-up' people do not know how to live the truth," he said. "And many times, we also experience the temptation of duplicity."

The pope urged Christians to hear Jesus' warning against duplicity and to ask themselves whether they practice what they preach: "Do we say one thing and do something else? Are we concerned only about showing how impeccable we are on the outside, made-up, or do we also cultivate our interior life in sincerity of heart?"

Among the visitors in St. Peter's Square was a group of people holding a banner with the colors of the Argentine flag, which read "Come Francis; your people await you."