St. Mamertus was the first to institute the Rogation Days. Through his prayer a fire that threatened to destroy the city was extinguished. The saint took occasion of this miracle to instruct the people on the necessity and efficacy of prayer.
In the midst of the congregation did the Lord open his mouth. And filled him with the spirit of wisdom and understanding. — Eighth Responsory
The Imitation of Christ
The kingdom of God is peace and joy in the Holy Ghost: which is not given to the wicked.
When the Rogation Days are kept, will you think that this saint is responsible for their institution? Their purpose is largely to ask God's blessing on the crops.
You think nothing of sitting down at table and having bread or vegetables, etc. Will you try to imagine a time when there would be no food? There would be none at all were it not for God's goodness to give fertility to the soil. So, when the Rogation Days come around, pray, and pray hard for God's blessing on the crops that you may not starve.
That Thou wouldst give the fruits of the earth and preserve them, we beseech Thee to hear us.