VATICAN CITY — Christians are called to be the salt of the earth, and if they don't share the flavor of their faith, hope and love with others, they are simply "museum Christians," Pope Francis said.

"Salt has meaning when it gives flavor to something. Salt kept in a bottle, with the humidity, loses its strength and is useless," he said May 23 in a homily during his early morning Mass in the chapel of the Domus Sanctae Marthae.

Pope Francis was commenting on Jesus' line from the Gospel of Mark: "Salt is good, but if salt becomes insipid, with what will you restore its flavor?"

Cardinals Angelo Sodano, dean of the College of Cardinals, and Leonardo Sandri, prefect of the Congregation for Eastern Churches, concelebrated the Mass, which was attended by employees of the Eastern Churches' office.

Pope Francis said God gives Christians flavor, or salt, in order for them to share it with others and make a difference in the world, he said.

"When salt is used well, you don't taste it. Salt improves the taste of the dish, making it better and helping preserve it."

One of the special characteristics of Christianity, he said, is that God gives each Christian different gifts and characteristics.

Christianity is not about uniformity, the pope said: "It takes each person as he is -- with his personality, his characteristics, his culture -- and leaves him with those, because they are riches. But it gives something more: It gives flavor."

Often, he said, Christians try to push for uniformity in the church; they want "everyone to be salted the same. But it would be like a woman who puts too much salt in a dish and you taste only the salt, not the food."

Pope Francis said God gave each person faith, gifts and talents so that they would share them with others and bring the taste of the Gospel to the world. Christians must "go out with the message, go out with the riches of salt that we have received and give it to others," he said.

At the same, he said, in order to maintain the flavor of the salt, Christians need to have a relationship with the one who gave it to them. Strengthened by prayer and adoration, Pope Francis said, the Christian witness and service to others ensures "we don't become museum Christians."

"Watch out, museum Christians. Salt without flavor is a salt that does nothing," he said.