"Rav Simlai came in front of Rav Yochanan and asked him to teach him Sefer Yuchsin, the Book of Lineage. He [Rav Yochanan] asked him where he was from. 'Lod,' he replied. 'And where do you live?' 'In Neharda'. 'We [Rav Yochanan responded] do not teach it, neither to Lodians or Nehardeim; how much more so to you, who are from Lod and reside in Neharda'" (Pesachim 62b).