Parallel passage: Luke 12:31, which is shorter. But; i.e. in contrast to such seeking as he has just spoken of. Our Lord at length gives a distinct promise that if God's cause is made the first aim, all the necessaries of life shall be provided.
Seek ye first. The difference between ζητεῖν here and ἐπιζητεῖν in Luke 12:32 seems to be only that the latter points out more clearly the direction of the search. First. If the search for earthly things be put into a secondary place, it may be allowable.
The kingdom of God, and his righteousness; his kingdom and his righteousness (Revised Version). "Of God" must almost certainly be omitted with א (B); of. Westcott and Hort, 'App.' The first phrase represents rather the external, the second the internal aim.
Seek ye the spread and accomplishment of God's kingdom; seek ye personal conformity to his standard of righteousness. Both thoughts are of fundamental importance for this "sermon" (kingdom, of. Matthew 5:3, Matthew 5:10, Matthew 5:19, Matthew 5:20; Matthew 6:10; righteousness, especially Matthew 5:17-20), which treats essentially of the way in which the subjects of the Divine kingdom should regard the Divine righteousness and conform to it.
And all these things shall be added unto you; of. the apocryphal saying of our Lord, repeated by Origen (Clem. Alex.), "Jesus said to his disciples, Ask great things, and the small shall be added to you; and ask heavenly things, and the earthly shall be added to you".