27 Whence, Venerable Brothers, did St. Boniface draw that tireless energy, that unconquered strength of soul whereby he could surmount so many difficulties, endure so many labors, overcome dangers, and struggle on behalf of Christ's kingdom even to the shedding of his blood and the martyr's crown? Without a doubt he drew it from divine grace, which he ever sought in humble, persevering and fervent prayer. So strongly was he driven by love of God that his one aim was an ever closer union with Him, an ever lengthier converse with Him; his prime purpose was to preach God's glory to unknown tribes, and to bring them to Him in reverence and love. He could surely repeat with every right that phrase of St. Paul's: "With us, Christ's love, is a compelling motive." And this other: "Who will separate us from the love of Christ? Will affliction, or distress, or persecution, or hunger, or nakedness, or peril or the sword?. . . Of this I am fully persuaded; neither death nor life . . . neither what is present nor what is to come, no force whatever, neither the height above us nor the depth beneath us, nor any other creature, will be able to separate us from the love of God, which comes to us in Christ Jesus our Lord."
Source: Ecclesiae Fastos (Vatican.va)