Is it permissible to take oaths while buying and selling if one is truthful?

Question 1: Is it permissible to make oaths while buying and selling if one is truthful?

Answer: Making oaths in buying and selling is Makrooh (disliked) in general, whether one is truthful or not. If a person lies in his oath then it is Makrooh in the sense of being Haraam (forbidden); the sin is greater and the punishment is more severe because it is a false oath… read more here.