How do believers in the tripartite nature of man (body, soul and spirit) explain Jesus' omission of the word "spirit" in Matthew 10:28?

Matthew 10:28: > 28 `And be not afraid of those killing **the body**, and are not able to kill **the soul**, but fear rather Him who is able **both soul and body** to destroy in gehenna. [YLT] > > 28 And fear not them which kill **the body**, but are not able to kill **the soul**: but rather fear him which is able to destroy **both soul and body** in hell. [KJV] > > 28 And do not fear those who kill **the body** but cannot kill **the soul**. Rather fear him who can destroy **both soul and body** in hell. [ESV] According to believers in the tripartite nature of man (body, soul and spirit, i.e., *trichotomism*), why did Jesus omit the word "spirit" in Matthew 10:28? Did Jesus expect his audience to have an understanding already of the fate of a person's spirit upon death, which is why he thought it unnecessary to say anything about the "spirit"? If so, what was that implicit understanding?