"Perhaps when you look at your hands they seem empty, perhaps you feel disheartened and unsatisfied by life. If so, do not be afraid: the Beatitudes are for you," the pope said.
"For you who are afflicted, who hunger and thirst for justice, who are persecuted. The Lord promises you that your name is written on his heart, written in heaven!" he stated.
"Today I thank God with you and for you, because here, where wisdom arose in ancient times, so many witnesses have arisen in our own time, often overlooked by the news, yet precious in God's eyes," he continued. "Witnesses who, by living the Beatitudes, are helping God to fulfil his promises of peace."
St. Joseph Cathedral, called Mar Yousef, was constructed in the 1950s, and restored in 2018 by Chaldean Patriarch Louis Raphaël Sako.
The cathedral can seat 400, but due to COVID-19 precautions, the Mass was limited to an attendance of 180 people.
In his homily, Francis encouraged Catholics to not try to be "occasional heroes, but to become witnesses day after day."
"Witness is the way to embody the wisdom of Jesus. That is how the world is changed: not by power and might, but by the Beatitudes. For that is what Jesus did: he lived to the end what he said from the beginning."
He pointed to the Scripture passage in 1 Corinthians 13, which says "love is patient," to remind Catholics that though people throughout history have been unfaithful to the covenant with God, and have fallen into the "same old sins," the "Lord always remained faithful."
"This patience to begin anew each time is the first quality of love," he emphasized, encouraging them to follow the Lord's example.
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God's witnesses are "not passive or fatalistic, at the mercy of happenings, feelings or immediate events. Instead, they are constantly hopeful, because [they are] grounded in the love that 'bears all things, believes all things, hopes all things, endures all things,'" he said.
"We can ask ourselves: how do we react to situations that are not right?" Francis said, explaining that "in the face of adversity, there are always two temptations" -- flight or anger.
But these two approaches never fixed anything, he said. "Jesus, on the other hand, changed history. How? With the humble power of love, with his patient witness. This is what we are called to do; and this is how God fulfils his promises."