2 And so, in the spirit of the Divine Master, We have directed a helpful word, now of admonition, now of exhortation, now of direction, to youths and to their educators, to fathers and mothers, on various points of Christian education, with that solicitude which becomes the common Father of all the Faithful, with an insistence in season and out of season, demanded by our pastoral office and inculcated by the Apostle: "Be instant in season, out of season; reprove, entreat, rebuke in all patience and doctrine." Such insistence is called for in these our times, when, alas, there is so great and deplorable an absence of clear and sound principles, even regarding problems the most fundamental.
Source: Divini Illius Magistri (Vatican.va)