What is the ruling on dealing with a brother who is suspected of earning unlawful money as a result of taking a false oath, and must he be boycotted?

A false oath sworn by a seller to market his goods is a major sin. In the Hadith, it is stated: "There are three whom Allah will not speak to on the Day of Resurrection, nor will He look at them, nor will He purify them, and for them there will be a painful torment: the one who lets his garment hang below his ankles [out of arrogance], the one who reminds others of his favors, and the one who sells his goods by a false oath." This oath in a sale does not affect the validity of the contract; the contract remains valid. The wronged buyer has the option to either uphold the contract or annul it. If the contract is valid, its effects take place, with the money transferring to the seller and the sold item to the buyer. The seller is sinful and disobedient to Allah, and he is treated like other disobedient individuals. The decision of whether or not to boycott him depends on what serves the greater good.