The Fathers generally interpret Jesus’ comments about the Pharisees as one might expect, emphasising that in devoting so much care to the externals of faith, they neglect its core; it is not about them and their status and power, it ought to be about their service to those who need them. When we err in that way, when we put so much emphasis on ceremony and externals and despise those who do not do as we think ought to be done, then we too fall into the error of the Pharisees.
Chtusostom emphasises the free nature of Grace, pointing out that if the Kingdom were for sale, then the poor widow would have received nothing large for her small donation. But since the Lord sees our intentions, she receives everything because he knows what is in her heart. In giving all she had, Jerome comments, she surpassed in her generosity any rich man. St Augustine draws our attention to the parallel with Zachaeus to drive hom the point that it is the manner of our giving and our intentions in giving which matter – the one was saved by giving half his wealth, the widow by giving all she had – what God heeds is our hearts and our faith.
Bede, always acute in his reading of Mark, adds that the:
treasure in one’s heart is the intention of the thought, from which the searcher of hearts judges the outcome. Hence it quite frequently occurs that some persons perform good deeds of lesser importance with a greater reward of heavently grace. This is because of the intention in their hearts to accomplish greater good if they could. Others, though they display greater works of virtue, are allotted smaller rewards by the Lord on account of the indifference in their lukewarm hearts.
God is the only only Just Judge, because he alone knows the devices and the desires of our hearts