8 Our saint, then, living for a long time this secluded and solitary life in the cave of Subiaco, shaped and set himself in sanctity, and laid those solid foundations of Christian perfection on which he was given later to raise a mighty building of lofty heights. As you well know, Venerable Brethren, zealous and apostolic works become useless and vain unless they proceed from a soul enriched with those Christian qualities which alone with God's grace can make human undertakings contribute to the glory of God and the salvation of souls. This Benedict knew well and had found to be true. Before undertaking and executing those great designs and plans to which he was called by God, he first devoted his most earnest efforts and fervent prayers to make himself fully master of that integral, evangelical holiness which he desired the others to acquire.
Source: Fulgens Radiatur (Vatican.va)