John 9:11 records the man's first testimony — the very account he refers to when he says 'I have told you already.' This cross-reference provides that prior statement.

John 9:15 is the man's second testimony before the Pharisees — the specific telling he says they ignored. It shows the repeated explanation that provoked his frustration.

In John 9:10, neighbors first ask about his healing — the man's exasperation in 9:27 refers to having explained it repeatedly since then.

John 7:47 has the Pharisees asking 'Have you also been deceived?' — the same dismissive 'also' pattern as the man's sarcastic 'Do you also want to become his disciples?'

Luke 22:67 shows Jesus similarly telling the Sanhedrin they won't believe if he tells them — both express frustration at willful unbelief despite being asked.