I only have holy bread for men who have not been around women. (21:4)
According to the note for this verse in The HarperCollins Study Bible, Ahimelech was referencing Exodus 19:15 here, which reads: "And he said unto the people, Be ready against the third day: come not at your wives."
I'm not sure I see the connection, though. Moses was telling the men to abstain from sex the night before God appeared to them on Mount Sinai. What does that have to do with "holy bread"?