There are innumerable opportunities open to the laity for the exercise of their apostolate of evangelization and sanctification. The very testimony of their Christian life and good works done in a supernatural spirit have the power to draw men to belief and to God; for the Lord says, “Even so let your light shine before men in order that they may see your good works and give glory to your Father who is in heaven” (Matt. 5:16).
However, an apostolate of this kind does not consist only in the witness of one’s way of life; a true apostle looks for opportunities to announce Christ by words addressed either to non-believers with a view to leading them to faith, or to the faithful with a view to instructing, strengthening, and encouraging them to a more fervent life. “For the charity of Christ impels us” (2 Cor. 5:14). The words of the Apostle should echo in all hearts, “Woe to me if I do not preach the Gospel” (1 Cor. 9:16)

-Pope Paul VI (Decree on the Apostolate of the Laity, 6)