Keep your promises and fulfill your vows no matter what they are or when they were made .

This hadith is about fulfilling vows. In the days of Ignorance, before Islam was revealed, 'Umar had vowed to spend one night in Itikaf. When he asked the Prophet about it, the Prophet commanded him to fulfill his vow and spend that night in Itikaf. This teaches us that we should always keep our promises and fulfill our vows no matter what they are or when they were made. We should also be honest with ourselves and others and not make promises we cannot keep or do not intend to keep. Furthermore, this hadith shows us that even if something was done before Islam was revealed it can still be valid if it does not contradict Islamic teachings or values.