18.19 . And in like manner We awakened them that they might question one another . A speaker from among them said : How long have ye tarried? They said : We have tarried a day or some part of a day , ( Others ) said : Your Lord best knoweth what ye have tarried . Now send one of you with this your silver coin unto the city , and let him see what food is purest there and bring you a supply thereof . Let him be courteous and let no man know of you .