Matthew 6:33

But seek ye first the kingdom of God, and his righteousness; and all these things shall be added unto you.
KJV
 

What is God's kingdom? John and Jesus both said at the start of their ministries that it was "at hand" (Matt. 3:2; 4:17). Jesus said that some in his generation would see the kingdom come (Mark 9:1). Daniel prophesied that the kingdom would come in the days of the Roman empire (Daniel 2:44). After Pentecost, Paul wrote that the members of the Colosse church had been translated into God's Son's kingdom (Colossians 1:13), and John wrote to the seven churches that Christ had made them a kingdom (Rev. 1:6) and that he was their brother and companion in the kingdom (Revelation 1:9). Therefore, the kingdom must be the church.

What is the church? The Greek is "ekklesia," which literally means an assembly. In the religious context, it means the universal assembly (Matthew 16:18) or the local assembly (Romans 16:16) of Christians.

So if the assembly (church - universal and/or local) is the kingdom of God...then what are we to seek first, i.e., make our top priority (Matthew 6:33)? The church, the assembly.

With that in mind, if the church meets for worship on a Sunday night, or Bible study on a Sunday morning or Wednesday night, or for a meal on Sunday afternoon, or a "work day" on Saturday afternoon, then if you could be there and yet choose not to be...are you truly "seeking first God's kingdom"? Of course not.

If the elders have decided that a congregation meets for Bible study twice a week and worship twice in a day, then seeking God's righteousness first would mean that one would obey Hebrews 13:17 and attend those assemblies. If one is in a congregation without elders, then seeking God's kingdom first would mean that one would do one's best to be there whenever the doors are open.

Harmonize this verse with Hebrews 10:25