We ask for what reason our Lord was unwilling to state the time of His coming (cf. Mk. 13:31-32). If we ask it, we shall not find it is owing to ignorance, but to wisdom. For it was not to our advantage to know; in order that we being ignorant of the actual moments of judgment to come, might ever be as it were on guard, and set on the watch-tower of virtue, and so avoid the habits of sin; lest the day of the Lord should come upon us in the midst of our wickedness.
Ambrose... the Apostle Peter declared that the Church was built by the Holy Spirit. For you read that he said: 'God, Who knows the hearts of men, bore witness, giving them the Holy Spirit, even as was given to us; and He made no distinction between us and them, purifying their hearts by faith' (Acts 15:8-9). In which is to be considered, that as Christ is the Cornerstone, Who joined together both peoples into one, so, too, the Holy Spirit made no distinction between the hearts of each people, but united them.
AmbroseIf you offer fasting with humility and with mercy, your bones, as Isaiah said, shall be fat, and you shall be like a well-watered garden (cf. Isa. 58:11). So, then, your soul shall grow fat and its virtues also by the spiritual richness of fasting, and your fruits shall be multiplied by the fertility of your mind, so that there may be in you the inebriation of soberness, like that cup of which the Prophet says: 'Your cup which inebriates, how excellent it is' (Ps. 23:5 LXX)!
Ambrose