Is writing or reciting poetry or an article without attributing it to its author considered theft?

There is no harm in quoting or transmitting from the words of others without mentioning their name, as long as the transmitter does not mislead others into believing it is his own creation. Scientific integrity requires attributing a statement to its author. However, if the writer or poet attributes what he has quoted to himself, this is forbidden deception and falsehood, and it may constitute an infringement on intellectual property if it is copyrighted material.