Speak truthfully even if you may lose something or someone else gains something from your honesty

This hadith explains that taking a false oath to deprive someone of their property is a sin and Allah will be angry with the person who does it. It was narrated by Abdullah bin Mas'ud, who said that the Prophet Muhammad ﷺ said, "Whoever takes a false oath to deprive somebody of his property will meet Allah while He will be angry with him". This was confirmed by verse 3:77 in the Quran which states, "Verily those who purchase a little gain at the cost of Allah's covenant, and their oaths." Al-Ashath came to where Abdullah was narrating this hadith and said that this verse was revealed concerning him. He explained how he had been in dispute over ownership of a well on land owned by his cousin. The Prophet asked for witnesses but Al-Ashath did not have any so he suggested letting the defendant take an oath instead. However, Al-Ashath feared they would take a false one so then this verse from the Quran was revealed confirming what Muhammad ﷺ had said about taking false oaths being sinful.

This Hadith teaches us that we should never take or give false testimony as it is considered sinful in Islam and displeasing to God. We should always strive for truthfulness even if it means we may lose something or someone else gains something from our honesty. We must also remember not to use our words carelessly as they can have serious consequences both here on earth and in our afterlife too!