Mark 12:7 But those husbandmen said among themselves, This is the heir; come, let us kill him, and the inheritance shall be ours.
But in this case the vine dressers spoke among themselves, Since this is the heir; come together, kill him, and the inheritance shall be ours.
The words used for "say" in this verse and the previous verse are different in Greek. The word used when the landowner speaks (legô) has more of a sense of statement. The word used to describe the vine dressers (eipon) has more of a sense of discussion. The two words translated simply as "this" describing the heir have the sense of justifying something (hoti=since, houtos=that is why).