Church Fathers on Matthew 6:21

When He has driven away the disease of vanity, He does well to bring in speech of contempt of riches. For there is no greater cause of desire of money than love of praise; for this men desire troops of slaves, horses accoutred in gold, and tables of silver, not for use or pleasure, but that they may be seen of many; therefore He says, 'Lay not up for yourselves treasure on earth.'

For if any does a work with the mind of gaining thereby an earthly good, how will his heart be pure while it is thus walking on earth? For any thing that is mingled with an inferior nature is polluted therewith, though that inferior be in its kind pure. Thus gold is alloyed when mixed with pure silver; and in like manner our mind is defiled by lust of earthly things, though earth is in its own kind pure.

Otherwise; As the Lord had above taught nothing concerning alms, or prayer, or fasting, but had only checked a pretence of them, He now proceeds to deliver a doctrine of three portions, according to the division which He had before made, in this order. First, a counsel that alms should be done; second, to shew the benefit of almsgiving; third, that the fear of poverty should be no hindrance to our purpose of almsgiving.