A.T. Robertson Commentary Luke 17:20

"And being asked by the Pharisees, when the kingdom of God cometh, he answered them and said, The kingdom of God cometh not with observation:" — Luke 17:20 (ASV)

With observation (μετα παρατησεως). Late Greek word from παρατηρεω, to watch closely. Only here in the N.T. Medical writers use it of watching the symptoms of disease. It is used also of close astronomical observations. But close watching of external phenomena will not reveal the signs of the kingdom of God.