Paul Cites Socrates

In Phaedo, Socrates says, "I am very far from admitting that he who contemplates existence through the medium ideas, sees them only 'through a glass darkly." Aside from the philosophical question he is exploring, Socrates is discussing his own impending death. Notice that McMahon (translator) has put this phrase in quotation marks. Notice, also, that this phrase is repeated in First Corinthians, Chapter 13. Was Paul quoting Socrates? Were they both quoting another source? Or, were they expressing a common place from their day?