Safeguards : Ethics of Our Fathers: Avot 3:13
Rabbi Akiva would say: Jesting and frivolity accustom a person to promiscuity. Tradition is a safety fence to Torah, tithing a safety fence to wealth, vows a safety fence for abstinence; a safety fence for wisdom is silence.
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Rabbi Ovadia Bartenura authored what most consider to be the pre-eminent commentary on the Mishna (somewhat like the commentary of Rashi has become to the study of Chumash - the Five Books of Moses). Colloquially it's referred to as "Bartenura."