It was narrated from Hafsah that the Messenger of Allah ﷺ said: "There is no fast for the one who did not make it incumbent upon himself from the night before".
This hadith also reminds us of the importance of being mindful and aware of our actions at all times, especially when engaging in acts of worship such as fasting. We should always remember that our intentions are important and can affect how our deeds are accepted by Allah. Therefore, we must ensure that we have a sincere intention whenever performing any act of worship or obedience towards Allah so that it may be accepted by Him.