One of the virtues of Siyaam (fasting) is that Allah the Almighty has selected a large gate in Jannah (Paradise) for its people, and only those who observe Sawm will enter through it on the Day of Resurrection. They will be called to be glorified and honored. 

Here is the Hadith where this virtue of Sawm is mentioned: 

(Sahl bin Sa'd (May Allah be pleased with him): The Prophet (peace be upon him) said, "In Jannah there is a gate which is called Ar-Raiyan through which only those who observe Sawm (fasting) will enter on the Day of Resurrection. None else will enter through it. It will be called out, "Where are those who observe fasting?" So they will stand up and proceed towards it. When the last of them has   entered, the gate will be closed and then no one will enter through that gate.")

[Al-Bukhari, Muslim, At-Tirmithi & An-Nasa'i]