"Haven't you read," he replied, "that at the beginning the Creator 'made them male and female,' and said, 'For this reason a man will leave his father and mother and be united to his wife, and the two will become one flesh'? (Matthew 19:4-5)
Thats a common reply Christians give and to be honest it's a very lame one, firstly we can be sure it's a metaphorical statement since two flesh cannot be ONE unless you went through some serious medical surgery secondly suppose we even took this ECHAD ( ONE ) to actually mean more then one then we will face some seriously problems that's if we use the analogy for all other statement found in the bible right ?? Let's see what we can make of this word ECHAD :
But they replied, "Your servants were twelve brothers, the sons of ONE man, who lives in the land of Canaan. The youngest is now with our father, and one is no more."
Son of ONE man (l.e Jacob ) shall we conclude the twelve brothers had more then ONE Father?? Let's carry on.
Now the LORD had said to Moses, "I will bring ONE more plague on Pharaoh and on Egypt. After that, he will let you go from here, and when he does, he will drive you out completely. (Exodus 11:1)
How many more plague were brought to pharaoh? Was that not the LAST "ONE" or were there more after ??? Since they all drowned and no more plague touched them let's carry on.
And Solomon's provision for ONE day was thirty measures of fine flour, and threescore measures of meal, (1 kings 4:22)
Now Solomons wealth in ONE day accumulated to such an amount? The question is does the ONE day mean ONE or more then ONE day? Wouldn't that really change his statue
Also note of one doesn't mean one. Then we can conclude a man can marry more then one wife? Since they very word one doesn't mean One it means more then One.
This is what Anthony buzzard had to say about ECHAD
There are some 970 occurrences of “one” (echad) in the Hebrew Bible. The word means “one and not more than one.” One single! The fact that one day has an evening and morning (Gen. 1:5) does not in any way alter the meaning of the word “one”! Do think this through carefully and show your children! “Abraham was one [echad] person” (Ezek. 33:24). What does that tell you about the plurality of Abraham?! Nothing. The language is exactly the same for God. Abraham and God are each “one p/Person”!