He went out into the mountains to pray (exelqein auton ei to oro proseuxasqai). Note ex- where Mark 3:13 has goeth up (anabainei). Luke alone has "to pray" as he so often notes the habit of prayer in Jesus. He continued all night (hn dianuktereuwn). Periphrastic imperfect active. Here alone in the N.T., but common in the LXX and in late Greek writers. Medical writers used it of whole night vigils. In prayer to God (en th proseuch tou qeou). Objective genitive tou qeou. This phrase occurs nowhere else. Proseuch does not mean "place of prayer" or synagogue as in Acts 16:13 , but the actual prayer of Jesus to the Father all night long. He needed the Father's guidance now in the choice of the Apostles in the morning.