Joining Text Cells

Hey guys I have an easy question that I cannot seem to figure out on my own. Here is an example of what I would like to do:

Lets say I have 3 cells A1,A2,A3...A1 is the word "the", A2 "brown", and A3 "dog". Now I would like cell B1 to join all of those words together to say "the brown dog". I am wonder what the proper formula is to display this. Thanks!