Quoting Source Material
There are many reasons for quoting source material, a primary one being that captured in the expression: "getting it straight from the horses mouth."
Quoting authoritative voices in your field lends credence to the arguments you present. By association, your words and those you quote are drawn closer together, creating powerful perceptions for you readers regarding the veracity and validity of your work.
It's especially important in academic writing that original sources be quoted accurately and correctly and that they be cited immediately following their appearance in the text.