5 The Lord Jesus Himself showed this also far more openly, when He companied on earth with His disciples during forty days after His resurrection; and having on the fortieth day ascended into heaven, did at the end of ten days send the wages, the Holy Ghost. These were done in signs, and by a kind of signs were the very realities anticipated. By significant tokens are we fed, that we may be able to come to the enduring realities. We are workmen, and are still laboring in the vineyard: when the day is ended and the work finished, the wages will be paid. But what workman can hold out to the receiving of the wages, unless he be fed while he labors? Even you yourself will not give your workman only wages; will you not also bestow on him that where with he may repair his strength in his labor? Surely you feed him to whom you are to give wages. In like manner also does the Lord, in those significant tokens of the Scriptures, feed us while we labor. For if that joy in understanding holy mysteries be withdrawn from us, we faint in labor, and there will be none to come to the reward.
Source: Tractates on the Gospel of John (New Advent)