VATICAN CITY (CNS) — Complaining is a poison that causes anger, resentment and sadness, and closes one’s heart to God, Pope Francis said.

“Let us ask in prayer for the grace not to waste time polluting the world with complaints, because this is not Christian,” the pope told those gathered in St. Peter’s Square Aug. 29 during his Sunday Angelus address.

“Jesus instead invites us to look at life and the world starting from our heart” because, by looking inside, people will find “almost all that we despise outside,” he said.

When people sincerely ask God “to purify our heart, that is when we will start making the world cleaner” because the best way to defeat evil is “by starting to conquer it within yourself,” the pope said.

The pope reflected on the Sunday Gospel reading from St. Mark in which Jesus explains why he does not follow some of the rituals of purification, saying God knows when people honor him “with their lips, but their hearts are far from me.” Jesus told the crowd that the things that defile people do not come from the outside world, but from within themselves, from their hearts and “evil thoughts.”

Pope Francis said, “this also pertains to us. We often think that evil comes mainly from the outside: from other people’s conduct, from those who think badly of us, from society.”

“How often we blame others, society, the world, for everything that happens to us! It is always the fault of ‘others,'” including those who govern, misfortune and so on, he said.

But all that time spent blaming others “is wasting time,” he said.

“We become angry, bitter and keep God away from our heart,” he said. “One cannot be truly religious in complaining: complaining poisons, it leads you to anger, to resentment and to sadness, that of the heart, which closes the door to God.”

The first step on the path of holiness, according to the first fathers of the church, was “to blame yourself,” the pope said.

“It is wisdom: learning to blame yourself. Try to do it, it will do you good. It does me good, when I manage to do so, but it is good for us,” he said. He prayed that Mary would help people purify their hearts by letting go of “the vice of blaming others and complaining about everything.”

After the Angelus, the pope greeted members of the Laudato Si’ Movement.

He thanked them “for your commitment to our common home, particularly on the World Day of Prayer for Creation” Sept. 1 and the Season of Creation that runs from Sept. 1 to Oct. 4.

“The cry of the earth and the cry of the poor are becoming ever more serious and alarming, and they call for a decisive and urgent action to transform this crisis into an opportunity,” he said.