II. Almsgiving and fasting are the most essential aids to prayer
And while all seasons are opportune for this duty, beloved, yet this present season is specially suitable and appropriate, at which our holy fathers, being Divinely inspired, sanctioned the Fast of the tenth month, that when all the ingathering of the crops was complete, we might dedicate to God our reasonable service of abstinence, and each might remember so to use his abundance as to be more abstinent in himself and more open-handed towards the poor. For forgiveness of sins is most efficaciously prayed for with almsgiving and fasting, and supplications that are winged by such aids mount swiftly to God's ears: since as it is written, “the merciful man does good to his own soul,” and nothing is so much a man's own as that which he spends on his neighbour. For that part of his material possessions with which he ministers to the needy, is transformed into eternal riches, and such wealth is begotten of this bountifulness as can never be diminished or in any way destroyed, for “blessed are the merciful, for God shall have mercy on them,” and He Himself shall be their chief Reward, who is the Model of His own command.
Source: Sermons (New Advent)