Sometimes Christians are able to take obedience and make it ugly; it’s one of our specialties.
In 1 Corinthians 16:5-8 Paul wrote about his plans to visit Corinth, but also acknowledged that the Lord must permit the visit or it wouldn’t happen. Paul wasn’t expecting an approved itinerary handed down to him by an angel from heaven, but he would recognize by providence if God allowed it.
Solomon wrote that “the heart of man plans his ways, but the LORD establishes his steps” (Proverbs 16:9). Only the LORD does “whatever” He pleases (Psalm 135:6); we are not the Lord.
Most Christians are probably familiar with James’ teaching about this perspective on providence.
Come now, you who say, “Today or tomorrow we will go into such and such a town and spend a year there and trade and make a profit,” … instead you ought to say, “If the Lord wills, we will live and do this or that.” (James 4:13, 15)
With all that in mind, in order to obey, do you need to say “if the Lord wills” before every stated intention or plan? Or, do you need to correct your brother or sister if they use a future tense verb without including the “Lord willing” qualifier?
James says that boasting in our self-determination is arrogant (James 4:16). It can also be arrogant to boast over a fellow-believer’s sentence structure. If he isn’t living in light of God’s control, then it might be good to bring it up, which is what James is doing. But Pharisees pay more attention to the proper use of formulas; what we need most is to live by faith.
How can you know if you are living James 4:15? You hold your schedule loosely. You respond to interruptions and changes with patience and contentment (which is harder than tagging sentences with Deo volente). You remember that “we have not even a moment in our power” (John Calvin, commentary on 1 Corinthians 16:7). You remember that your life is a mist, and that the Lord wills where it wafts and for how long.