Just say a simple, ‘Yes, I will,’ or ‘No, I won’t.’ Anything beyond this is from the evil one. Mat 5:37. Your word is your word! You don’t need to use persuasion or swear against something to add weight to what you’re saying. Who you are should be enough. The integrity of your words should be sufficient. If you say ‘yes’, then it is ‘yes’. God in you should shine through you in how you deal with others and in every commitment you make. If there’s a problem and something changes, then be clear and honest about the facts and communicate them quickly to those effected, who should more often than not, be understanding. You’re God’s ambassador in the world, people listen to what they see you do, more than to what you actually say, so get a reputation for being scrupulously reliable and God will be honoured in all that you do. Praise God today that He can not lie and that His word will never change.