Riyad Us-Saliheen (Gardens of the Righteous)

Chapter 318
Abomination of Swearing in Transaction

1720. Abu Hurairah (May Allah be pleased with him) said: I heard the Messenger of Allah (PBUH) saying, "Swearing produces a ready sale for a commodity, but blots out the blessing.''
[Al-Bukhari and Muslim].

Commentary:  What is meant here is that if a person takes an oath while offering a merchandise, he may succeed in selling a large quantity of it, but this is not a fair means of business because it increases the sale but robs the business of its blessings. Therefore, even if a person is perfectly right in his statement in respect of his merchandise, he should not take an oath to influence his customers.

1721. Abu Qatadah (May Allah be pleased with him) said: I heard the Messenger of Allah (PBUH) saying, "Beware of excessive swearing in sale, because it may promote trade but this practice will eliminate the blessing.''
[Muslim].

Commentary:  This Hadith also mentions the same thing which has been stated in the preceding Hadith. It has food for thought that when oath robs the deal of its blessing, even if one's oath is perfectly true, how great a sin those commit who take false oaths to sell their goods! May Allah save us from committing this sin.