I Corinthians 12:12-14, 19-20

For as the body is one and has many members, but all the members of that one body, being many, are one body, so also is Christ. For by one Spirit we were all baptized into one body—whether Jews or Greeks, whether slaves or free—and have all been made to drink into one Spirit. For in fact the body is not one member but many.

And if they were all one member, where would the body be? But now indeed there are many members, yet one body.