This is the 3rd time the Scriptures record YeHoVaH appearing to Abraham.  YeHoVaH and the men with Him had their feet washed and were served bread, butter, milk and beef.  Ironically, consuming meat and dairy products (including cheese) together is forbidden by Kosher dietary laws.YeHoVaH said that He would certainly return unto them according to the time of life and Sarah would have a son.  Sarah’s faith was not in the same place as Abraham’s faith. Sarah had a difficult time, if not impossible time, trusting that YeHoVaH could bring forth a child from her, being beyond childbearing age, and through Abraham who also was old.