Dear noble brothers, I have a glad tiding for you. If a man's debts reach 30 millions, his house is foreclosed, he is house arrested, he is sued in the court of law and he might be imprisoned, which means that he is in great trouble, but someone said to him, "If you do this matter for 30 days, your debts will be forgiven, so what do you say?" Will he hesitate for even one second? 

(Abu Hurairah (May Allah be pleased with him) reported: The Prophet (PBUH) said, "He who observes fasting during the month of Ramadan with Faith while seeking its reward from Allah, will have his past sins forgiven.")

[Agreed upon, on the authority of Abi Hurairah]

Much in the same line, if your sins are like mountains, they will be forgiven by fasting this month as Allah decrees, namely, a fasting that is full of acts of obedience, not a fasting that is spent on watching TV series, a fasting that is an act of worship, not a fasting that is a habit, a fasting of Taqwa not a fasting of committing sins and a fasting of giving in to Allah not a fasting of turning away from Him.

("He who observes fasting during the month of Ramadan with Faith while seeking its reward from Allah, will have his past sins forgiven.")

[Agreed upon on the authority of Abi Hurairah]

﴾ Nor does he speak of (his own) desire* It is only an Inspiration that is inspired.﴿ 

 [An-Najm, 3-4]