57 Relying on this hope, to you and to the flocks committed to your care We most lovingly grant in the Lord, as a token of divine gifts and a sign of Our special good will, Our Apostolic Benediction. Given at St. Peter's, in Rome, June 29th, the feast of the Holy Apostles Peter and Paul, in the year 1958, the 20th of Our Pontificate.
Source: Ad Apostolorum Principis (Vatican.va)