After describing the character of the kingdom in the Beatitudes and the call to be salt and light in Matthew 5, Jesus pivots in chapter six to the practice of the kingdom. He does not begin with a new command. He begins with a warning about motive. The verb translated “to be seen” comes from the same root that gives us our word theater. Disciples, Jesus says, are not actors on a stage. The danger is not that we will stop doing righteous things. The danger is that we will keep doing them for the wrong audience.
Notice how subtle this trap is. Jesus does not address obvious sin here. He addresses obvious good. Giving to the poor, prayer, fasting. These are the very acts that mark a serious disciple. Yet the same act can be done with two entirely different hearts. As D.A. Carson and Craig Blomberg both note in their commentaries, the higher righteousness of the kingdom touches not only what we do but the audience for whom we do it. Jesus is teaching us that without a transformed motive, even our most religious acts will leave us spiritually empty.
Compare this carefully with Matthew 5:16, where Jesus told the same disciples to let their light shine before others. There is no contradiction. A.B. Bruce captured it well when he said we are to show when tempted to hide, and to hide when tempted to show. Both commands aim at the same target. The glory goes to God. Public goodness glorifies God when it reflects his character in his people. Hidden piety glorifies God when it refuses to divert the glory to ourselves. The question is never simply, did anyone see? The question is, whom was I performing for?