39 "Behold, now is the acceptable time; behold, now is the day of salvation."(38) These are words which We consider most applicable to that period of time which will shortly be upon us when the Ecumenical Council is in session. But when God in His Providence decrees to give His supernatural gifts to men, He does so in the measure of their own individual desires and dispositions. Hence Our long-continued insistence on the spiritual preparation of Christians for this great event. Hence, too, the supreme importance of giving heed to this final invitation of Ours addressed to those who are willing to be guided by Our demands.
Source: Paenitentiam Agere (Vatican.va)