Festal.
The fountains of the Lord's kindness are ever gushing forth with good things for them that believe; but some further good is conveyed by the celebrations which preserve the memory of the greatest of benefits to them that keep the feasts with more good will. We have just now celebrated the rites and enjoyed their blessing, and thus salute your piety, for so the custom of the feast and law of love enjoins.
Source: Letters (New Advent)