“Look with favor on these offerings and accept them as you once accepted the gifts of your servant Abel.” (1st Eucharistic Prayer)
In a homily, St. Ambrose explains why God accepted Abel’s gifts and not Cain’s. His gifts were a prayer from his heart.
He brought them to God prompted by the same gratitude that caused the Samaritan to give thanks to Jesus after being cured of leprosy. Gratitude is always at the heart of the Eucharist.
Abel’s gifts were the result of true prayer, according to Ambrose, who summarizes what true prayer is: “Jesus told us to pray urgently and often, so that our prayers should not be long and tedious but short, earnest and frequent. Long elaborate prayers overflow with pointless phrases, and long gaps between prayers eventually stretch out into complete neglect.
Next he advises that when you ask forgiveness for yourself then you must take special care to grant it also to others. In that way your action can add its voice to yours as you pray. The apostle also teaches that when you pray you must be free from anger and from disagreement with anyone, so that your prayer is not disturbed or broken into.
The apostle teaches us to pray anywhere, while the Saviour says Go into your room – but you must understand that this “room” is not the room with four walls that confines your body when you are in it, but the secret space within you in which your thoughts are enclosed and where your sensations arrive. That is your prayer-room, always with you wherever you are, always secret wherever you are, with your only witness being God.
Above all, you must pray for the whole people: that is, for the whole body, for every part of your mother the Church, whose distinguishing feature is mutual love. If you ask for something for yourself then you will be praying for yourself only – and you must remember that more grace comes to one who prays for others than to any ordinary sinner. If each person prays for all people, then all people are effectively praying for each.
In conclusion, if you ask for something for yourself alone, you will be the only one asking for it; but if you ask for benefits for all, all in their turn will be asking for them for you. For you are in fact one of the “all.” Thus it is a great reward, as each person’s prayers acquire the weight of the prayers of everyone. There is nothing presumptuous about thinking like this: on the contrary, it is a sign of greater humility and more abundant fruitfulness.”