The historical Third Commandment is a point where the Talmadic and Philonic divisions meet, "Thou shalt not take the name of the Lord thy God in vain; for the Lord will not hold him guiltless that taketh his name in vain." (Exodus 20:7); according to the Augustinian division this is the Second Commandment. Historically, as Felder points out, this has taught to children as to not swear or curse. Further examples are used, which are a more mature application, that one should not make promises or condemnations ("I swear to God", "Damn you") with Divine invocations unless they are treated with appropriate seriousness - after all, this is the Divine and inner core of a person that is being put on the line here. It would have been appropriate here to also mention the historical and Biblical link between testify (attest, testament, contest etc) and testes.