Spend enough time in Christian circles and you'll inevitably have disagreements with other Christians over points of theology and hermeneutics. In most cases you can respectfully agree to disagree, but occasionally they are so clearly in the wrong that they need to be corrected. Often it's in seeing how other Christians misuse Bible verses that you discover what they actually mean.
Matthew 6:3 is a good example of one such verse, which reads as "But when you give to the needy, do not let your left hand know what your right hand is doing." (NIV)
I recently heard of someone who asserted to another Christian that because the left hand is the "unclean" hand, as it was in certain cultures in ancient times, this verse teaches that it is sinful to use your left hand to put money in the offering plate when it's passed around. The mind boggles at how the individual concerned could make such a radical interpretation.
This teaching is part of the Sermon on the Mount. To get the context of a verse, you need to read the verses before and after it. The context of this verse is part of a discourse in Matthew 6:1-18 contrasting true piety with hypocritical piety. Here, Jesus was speaking about religious leaders who gave to the needy not out of a desire to help them, but so that others would think well of them. In verse 2 he called them "hypocrites." Hypokrites is a Greek term for stage actors who wore masks to play various roles. Their giving was part of a facade, to disguise the fact that their hearts were far from God (cf Matthew 23:25-26).
The trumpets that Jesus speaks of may refer to actual trumpets, which were used to announce an especially large gift being given, or he may be referring to the sound of coins being tossed into the trumpet-shaped money chests in the temple used for collecting alms. One of the commentaries I looked at briefly mentions a reference in the Mishnah to a room in the Temple where benefactors could leave their gifts to the poor anonymously.
In verse 3 Jesus was clearly using a figure of speech to make a point about having a humble attitude when giving, to give out of pure motives, solely out of concern for the poor, and to not do it to make yourself look good. Good works have their place but they are of little use if they're done with the wrong motives. As any good Bible scholar would tell you, there is no possible way to support the interpretation given in my anecdote.