Without spiritual courage and a love for Jesus, the word of God will be proclaimed as just "a good, philosophical or moral idea," Pope Francis said.
A preacher "may say something interesting -- something moral, something that will make you feel good, a philanthropic good -- but there is no word of God," the pope said during Mass in the chapel of Domus Sanctae Marthae.
In his homily Feb. 14, the feast of Sts. Cyril and Methodius, Pope Francis said the world needed missionaries and "brave heralds" of the Gospel like the two great evangelists and co-patron saints of Europe.
Reflecting on the day's first reading from the Acts of the Apostles, in which Paul and Barnabas announce the good news to the Gentiles, the pope said the word of God must be preached with "frankness and strength."
He also commented on the day's Gospel of St. Luke in which Jesus sends out 72 disciples to preach the good news, noting that Jesus highlights how necessary it is for those who preach the Gospel to also pray.
"The harvest is abundant, but the laborers are few; so ask the master of the harvest to send out laborers for his harvest," Jesus said.
The pope explained that Jesus' words express the importance of prayer when planting the seed of God's word so "that the Lord may water this seed and it may sprout."
"Without prayer, you can have a beautiful conference, a beautiful instruction: good, good! But it is not the word of God. The word of God can only come from a prayerful heart," he said.
Jesus' command for preachers to "go as lambs among wolves," the pope said, reminds Christians that a "true preacher is one who knows he is weak, who knows he can't defend himself."
Citing St. John Chrysostom, Pope Francis said if a preacher goes as "a wolf among wolves, the Lord will not protect you; you will defend yourself alone."
"When a preacher believes he is too intelligent or when the one who has the responsibility of bringing the word of God forward wants to be crafty," it does not end well, he said.
Like the patron saints of Europe, Christians are called to continue the mission of the great heralds of the church, "who have sown and helped make the church grow in the world" through prayer and humility.
"May Sts. Cyril and Methodius help us to proclaim the word of God," Pope Francis said.