Is it morally wrong to commit to do something?

Question: My friend claims that it is morally wrong to commit to do something, but that you always have to say "I'll try to do..." To me when they say "I'll try" it sounds like they are giving a half-hearted attempt to do something. But he says that he fully intends to do it and they just can't say "I'll do..." because if something happens and he can't do it, then it is a lie. In the Bible I found this verse: "Simply let your 'Yes' be 'Yes,' and your 'No,' 'No'; anything beyond this comes from the evil one." --- Matthew 5:37. From this verse I feel like it is saying that we should say that we will or won't do anything and that our maybe's come from the devil. Am I missing something? Are there any other scriptures that you can lead me to?

Good question. First, let me say that the point of Matthew 5:37 was to preclude the use of oaths or promises as a guarantee that you are telling the truth not to rule out the use of tentative words like maybe, perhaps, and hopefully. Jesus basically says, that we should always be telling the truth. All promises and oaths indicate that honesty is not our normal way of speaking and living. It is also true that the verse in Matthew 5 may be emphasizing caution and commitment. Be careful what you say 'yes' to and what you say 'no' to. It is important to know what God wants you to do (and not to do) and it is important to be a person of your word. If I have a reputation for being a person who does what I say I'll do, then a simple “Yes” or “no” is sufficient. Saying that, I do understand that there are sometimes things that are beyond our control that happen and change our ability to do what we say. For instance, "I'll help at the school tomorrow" and then, you get the flu and cannot help out. You were still sincere when you committed, but were not able due to circumstances beyond your control.

I think the scriptural principle that your friend is alluding to when he warns against definitive statements, is found in James 4:13-17
13Come 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"— 14yet you do not know what tomorrow will bring. What is your life? For you are a mist that appears for a little time and then vanishes. 15Instead you ought to say, "If the Lord wills, we will live and do this or that." 16As it is, you boast in your arrogance. All such boasting is evil. 17 So whoever knows the right thing to do and fails to do it, for him it is sin. (ESV)

Here it is clear that the purpose is not to forbid being decisive, or committed, but to forbid the arrogance of thinking we can plan our life (either strategically or tactically) while effectively excluding God and his plan for us from the process. The key is not to be legalistic, but to consistently seek God's will and do what you commit to do, in the strength and grace that Jesus provides.

Your friend sounds sincere in his/her concern, but seems to have missed the real intent of this passage. When my son asks me if I will pick him up after practice, I am not going to say, "I'll try." If an earthquake or a car breakdown prevents me from getting him, I am sure it is not sin and I know he is not viewing me as lacking in integrity. When my wife asks me if I will be home for dinner, I don’t hesitate to say yes, though there are times when other things prevent me – and we are not at odds because of it. The Bible doesn’t teach us to avoid commitment, but to keep the commitments that we make; honoring God and loving people in the process.