Gevurot Meyruach Hakodesh 7:5

And HASHEM did not give to him a nachalah (inheritance) in it nor AD MIDRACH KAF REGEL (even enough to put your foot on); and yet, even when he had no ben, the havtachah (promise) of HASHEM to him was ES HAARETZ HAZOT E'TEN (This land I will give) to him and to his zera (seed) after him.