Does the following sentence have an antecedent? If so, where?: Matt said that he likes riding his bike every morning.
There is one! Matt is the antecedent of he.
An antecedent is a word in a sentence which is referred to by a pronoun. This specific pronoun (though it could also be a pro-adverb or pro-verb, among other things) is called a proform.
As we see in the sentence, Matt is talking about himself. The person who is talking is the same person who likes riding his bike every morning. Repeating the antecedent not only sounds awkward, but also confuses the reader as they try to figure out who, or what, the subject is. It also obscures how actions in a sentence relate to the subjects. By avoiding these, antecedents and proforms help make a sentence more cohesive and fluid.