VATICAN CITY — On the Solemnity of the Most Holy Trinity, Pope Francis said unity is essential to Christian life because God is a communion of love.

“This mystery of the Trinity was revealed to us by Jesus himself,” Pope Francis said in his Angelus address on May 30.

“He showed us the face of God as a merciful Father; he presented himself, true man, as the Son of God and Word of the Father; he spoke of the Holy Spirit who proceeds from the Father and the Son, the Spirit of Truth.”

Speaking to pilgrims gathered in St. Peter’s Square from the window of the Vatican’s Apostolic Palace, the pope said that Trinity Sunday “makes us contemplate this wonderful mystery” and poses an invitation to grow in the “unity to which Jesus calls us.”

“And this unity I dare to say is essential to the Christian ... because it is the unity that is born from love, from the mercy of God, from the justification of Jesus Christ and from the presence of the Holy Spirit in our hearts,” he added.

Pope Francis said that “love is essentially a gift of self” which reflects the “infinite reality” of the Holy Trinity in which the “Father gives himself by generating his Son, who in turn gives himself to the Father, and their  mutual love is the Holy Spirit, the bond of their unity.”

Speaking off-the-cuff, the pope added that it may not be easy to understand the mystery of the Holy Trinity, but it is possible for everyone to “live this mystery.”

After praying the Angelus prayer in Latin with crowd in front of St. Peter’s Basilica, the pope announced that he has invited Christian leaders from Lebanon to the Vatican on July 1 to pray together for “the worrying situation in the country.”

The pope also celebrated the beatification of three Spanish Civil War martyrs, María Pilar Gullón Yturriaga, Octavia Iglesias Blanco, and Olga Pérez-Monteserín Núñez, which took place in Spain on May 29.

“These three courageous lay women, in imitation of the good Samaritan, dedicated themselves to treating the war-wounded and did not abandon them in the moment of danger. They took risks, and were killed in hatred of their faith. We praise the Lord for their evangelical witness,” he said.

Pope Francis aencouraged people to read the Bible to find the strength needed for life.

The pope said: “Always carry the New Testament with you, a pocket Gospel: in your purse, in your pocket, to be able to read it at any time of the day. Thus we will find Jesus in Sacred Scripture.”