Alfred Schlert, bishop of the Diocese of Allentown, offered a summary about the Trinity online Sunday as the Church marked the feast of the Holy Trinity.

The mystery of the Holy Trinity is a key part of the Catholic faith. At its core, it says that there is only one God, but three divine persons: God the Father, God the Son and God the Holy Spirit, Catholic Culture explains. God the Son, or Jesus, was begotten from the Father, and the Holy Spirit proceeds from both the Father and the Son. 

“When we think of the Holy Trinity, we often think back to our third-grade classroom where we learned that God is one God in three Divine Persons,” Schlert wrote online. “Just as in third grade, we still struggle to comprehend the Holy Trinity. Despite our incomprehension, the love present in the Holy Trinity penetrates every moment of our daily lives.” 

Catholics mark the feast of the Holy Trinity, a celebration that Britannica says dates to as early as the 10th century, on the Sunday after Pentecost Sunday. 

Schlert summed it up this way. “God the Father, the creator of Heaven and Earth created the Earth and all that is in it for our benefit. Jesus, the Son, came to reveal the love of the Father and offer Himself to the Father as a sacrifice for our sins. The Holy Spirit, whom the Father sent after Jesus' Ascension into Heaven, fills the Church with guidance and courage.” 

Pope Francis sent out a couple of tweets about the Trinity.

”The #MostHolyTrinity teaches us that a person can never be without the other," the pope said in a tweet. "We are not islands, we are in the world to live in God’s image: open, in need of others and in need of helping others.” 

In another, he added, "If we can truly invoke God, calling him ‘Abba — Dad,’ it is because the Holy Spirit dwells in us; he is the One who transforms us deep within and makes us experience the soul-stirring joy of being loved by God as his true children.”