NOTES for Rom 2:1-2
In denouncing sins, Paul points to the danger for the one who denounces: he risks sinking into the very same sins that he denounces in those around him. And all the more should people who do the very same things they have undertaken to denounce not judge the sins of others. In fact, a person often tends to accuse others precisely of the sins to which he himself is inclined.
Many people might object to this by saying that they condemn because they themselves are not like that. But let us remember how easily Peter fell in a way he did not suppose himself capable of. Persistence in sins, of which Paul writes, may show itself, among other things, in an unwillingness to see one's own sins.
One way of resisting one's own sinfulness can be constancy in good works, and Paul does not simply call for doing them from time to time, but writes specifically about constant doing. Is this possible for human beings? Generally speaking, no. But "what is impossible with men is possible with God" (Luke 18:27).