What does Matthew 6:3 mean?

Jesus has been clear: those who do otherwise good things with wrong motives should not expect any reward from God (Matthew 6:1–2). This follows His earlier teachings, from chapter 5, which explained that attitudes can be just as sinful as actions. In fact, as this passage shows, selfish motivations can even take the "good" out of "good deeds." His current example is giving to the needy in order to be praised for spirituality and generosity. Jesus called people with such motivation hypocrites.

Here, He gives the correct model for Christian giving to meet the needs of others: secrecy for the sake of authentic integrity. Once again using hyperbole—meaning "exaggerating for effect"—Jesus tells His audience not even to let their left hand know what their right hand is doing when giving to the needy. This emphasizes the level to which Christians need to avoid letting worldly praise motivate their actions. It also suggests that we can be just as motivated by egotism, meaning praise from ourselves to ourselves, as by the admiration of other people.

As in the prior verse, Jesus says "when" and not "if" you give to the needy. Disciples of Jesus should expect themselves to give in order to meet the needs of those who are truly lacking.