The two key words in this verse, the ones translated as "joined together" and "put asunder/separe" are used by Jesus only in this verse and its parallel in Matthew 19:6. Jesus commonly uses two other Greek words to mean "join" and "divide."
The humor here is in the word translated as "joined." which means "yoke together" and "harness together" and in yoking a team of mules or oxen to a plow or wagon. The root word means the "yoke" used for draft animals. and also, a pair of balances.
The "man" here is the same word describe what was made in the image of the Divine and could be translated as "mankind" or "humanity." It is also the "man" who leaves his parents to take a wife.
The Greek word for "put asunder/separate" is not the word that Jesus used to refer to divorce. The word Jesus uses to mean "divorce" is the Greek word meaning "to untie" or "to loosen." This word can mean "divorce," but it is never used in the Bible. It is usually used to mean "depart" or "separate." The root word is a noun that refers to the space between or around things. Its literal meaning is "to make space."
Christ's Words in Matthew as a Guide to 40 Days of Prayer.