Commentaries:
Robertson's Word Pictures (NT)
As he was praying (en tw einai auton proseuxomenon). Common Lukan idiom of en with the articular infinitive for a temporal clause, only here Luke has the periphrastic infinitive (einai proseuxomenon) as also in Luke 11:1. This item about Christ's praying alone in Luke.
Alone (kata monav). In the N.T. only here and Mark 4:10. Perhaps xwrav (places) is to be supplied with monav (lonely places).
Were with him (sunhsan autw). This seems like a contradiction unless "alone" is to be taken with sunhsan. Westcott and Hort put sunhnthsan in the margin. This would mean that as Jesus was praying alone, the disciples fell in with him. At any rate he was praying apart from them.
Other Robertson's Word Pictures (NT) entries containing Luke 9:18:
Mark 8:27
John 6:69
John 17:1
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