Unclear question. However, I inferred you are referring to story "Julius Caeser" by Shakespeare.
Answer:
<u>He rejected the proposal initially</u>.
Explanation:
Remember that Cassius was among the conspirators who wanted <em>Caeser</em> dead.
So he tried persuade Brutus to join them in their plot to kill Ceaser. However, after the conversation Brutus wasn't affected to join them at that moment.
