This paragraph assumes that disciples give to the poor (compare 6:19-24 at greater length); what it evaluates is how we give to the poor.
Jesus again employs hyperbole in his descriptions (as in 5:19, 29-30), thereby adding graphic force to his warnings. Although some scholars have argued that people actually blew trumpets during giving in the synagogues, Jesus probably simply uses rhetorical exaggeration to reinforce his point, as when picturing the Pharisees who swallow a camel whole but strain out a mere gnat (23:24). Jesus adds to this stark image still another: we should be so secretive in giving that we should not let our left hand know what our right hand is doing (6:3; 1 Cor 4:3-5). He challenges us about the danger of public piety with such forceful language precisely "because our assurance that such hypocrisy is no great problem with us is a major part of the problem" (Tannehill 1975:85).
Jesus emphasizes future reward for those who forgo present honor. He promises something better than a charitable deduction on one's income tax, nice as that may be (vv. 1, 2, 4). Many of his contemporaries believed that charity delivers the giver from death and stores up treasure in heaven (Tobit 4:10; 12:8; 14:10; t. Pe'a 4:21; Pes. Rab. 25:2); Jesus likewise emphasizes heavenly reward for serving those truly in need (6:19-21). In contrast to nineteenth-century evangelicalism, much of today's church is divided between those who emphasize personal intimacy with God in prayer and those who emphasize justice for the true poor (see Sider 1993). Like the prophets of old, however, Jesus demanded both (6:2-13; Mk 12:40); he also recognized that without keeping God himself in view, we can pervert either form of piety.
We should care for the poor. The phrase when you give to the needy implies the expectation, standard in Judaism, that one would care for the needs of the poor (Tobit 4:7), just as the phrase when you pray (6:5) takes for granted that the hearer will pray (m. 'Abot 2:10). Jesus' Jewish contemporaries emphasized that one must give charity from the right kind of heart (m. 'Abot 5:13) and sometimes objected to ostentation in charity (Test. Job 9:7-8; m. Seqalim 5:6).
If more of us Christians feared God, this realization would scare some sense into us. We like to think that Jesus was condemning the "legalistic" religion of Judaism, but we are wrong. Jesus was not condemning an officially legalistic religion, but the ostentatious practice of those whose religion taught purity of heart. In other words, on many points the Pharisees believed the same things we do, the same things Jesus was teaching. When we parade up to the altar to give our money (in some churches) or make sure the ushers see us contribute a significant offering when they pass the plate (in other churches), our hearts stand condemned regardless of our doctrine. True religion demands sufficient faith to settle for God's approval, to do what pleases him no matter what others may think.