When we speak of the merits of something (fadl or fadail), we are actually saying the deeds in it are highly recommended and the reward and benefits highly emphasized and guaranteed. I would like to cite several Ahadith that address this issue of fadail, merits of fasting during Ramadan, and filling the entire month with more 'ebadah than any other month.
Abu Hurairah (RA) relates the Messenger of Allah (SAW) said when one Ramadan came:
"A blessed month has arrived. Observing it in fasting is mandated on you (the believers). During this month, the gates of Paradise will be opened and the gates of Hellfire will be closed. The evil ones (Shayaatin) will be handcuffed. In it there is one night, during which worship is better than worship in a thousand months. Whoever is denied its blessings has been denied the biggest blessing." (Ahmed, Nasaae, and Bayhaqi)
This hadith is similar to the previous one, except that it emphasizes the importance of being mindful and aware of the rules that govern the 'ebadah of fasting. For one of the key words in every 'ebadah is "muwafaqah Ash-Shari'ie," observing in accordance to the commands of the Lawgiver.
(Extracted from The University of Southern California (USC) Muslim Students Union)