The Order to Fast

In an address to the believers of this Ummah, Allah ordered them to fast, that is, to abstain from food, drink and sexual activity with the intention of doing so sincerely for Allah the Exalted alone. This is because fasting purifies the souls and cleanses them from the evil that might mix with them and their ill behavior. Allah mentioned that He has ordained fasting for Muslims just as He ordained it for those before them, they being an example for them in that, so they should vigorously perform this obligation more obediently than the previous nations. Similarly, Allah said:

لِكُلٍّ جَعَلْنَا مِنكُمْ شِرْعَةً وَمِنْهَـجاً وَلَوْ شَآءَ اللَّهُ لَجَعَلَكُمْ أُمَّةً وَحِدَةً وَلَـكِن لِّيَبْلُوَكُمْ فِى مَآ ءَاتَـكُم فَاسْتَبِقُوا الخَيْرَاتِ

Commentary

Literally, Sawm صوم means to abstain'. In the terminology of Islamic law, Sawm صوم means 'to abstain from eating, drinking and sexual inter-course; with the conditions that one abstains continuously from dawn to sunset and that there is an intention to fast'. Therefore, should one eat or drink anything even a minute before sunset, the fast will not be valid. Similarly, if one abstained from all these things throughout the day but made no intention to fast, there will be no fast here too.