We may not [accept] measure[ments] except from an expert. If he extended [the techum] at one point and shortened it at another, the extended [techum] is followed. If one extended [it] while another shortened [it], the one who extended [it] is followed. Even a male slave, even a female slave is believed to say, ‘Until here is the Sabbath techum.’’ For the Sages did not state this law to be stringent but rather to be lenient.