Talk is Not cheep – No speech, no effect:

King David states that “the stone which has been repulsed by the builders will become the cornerstone.” Stones in this verse refers to the letters of speech. The letters of speech are lower than intellect or emotions, although do contain an advantage over them as they elevate the emotions and intellect to a level higher than wisdom. On this our sages state that thought alone does not accomplish anything, and hence Torah study is only effective if it is spoken. Just as a person cannot live without a house which is made from stones so too a person cannot serve G-d without the letters of speech of Torah.