The holy Prophet (s.a.) has said: "Ramadan is the month of GOD and the month of repentance."
He recited this prayer each day of Ramadan: "O GOD! This is Ramadan and the month of repentance."
The great leader of the Islamic revolution Imam Khomeini has written in Forty Hadith (40 sayings) that repentance is the referral from the nature to the self-spirit after that the glory of spirit was being veiled in the darkness of nature because of the sins and the disobedience.
GOD loves the penitents. The prophets always invited men to penitence which is a way toward evolution and gaining the true completion. Penitence is the most beautiful and vivid ways to make an apology.
In a narration the holy Prophet (s.a.) has said: "In the first night or Ramadan GOD orders the angels to prepare and arrange the heaven for those who fast and close the doors of hell to them and do not open them till the end of this month and he orders Gabriel to descent on earth and closes the path of devil to the nation of Mohammad in order that he (devil) cannot corrupt their faith and fasting."
Although there is always a way for repent and referral to GOD but Ramadan is the spring for repent. In this month its acceptance is vastly provided.
And again the holy Prophet (s.a.) has said in another saying that: "GOD asks during Ramadan, is there anyone who wants his repent to be accepted?"
Imam Khomeini has written in Forty Hadith that:
"My dear, do not pass by this stage nonchalantly and indifferently! Meditate and reflect over your condition and your ultimate end. Turn to the Book of God, the traditions of the Seal of Prophets and the Imams of guidance- upon all of whom be God's salutations- to the utterances of the 'ulama of the ummah as well as to the dictates of your own intellect and conscience. Do open this door, which is the key to all other openings, and enter this house which, for us, is the main abode of humanity. Consider it important and attend to it with care. Implore God, the Exalted and the Blessed, to grant you success in finding your cherished goal. Seek help from the spiritual station of the Noble Messenger and the Imams of guidance- upon all of whom be peace- and seek refuge in the Wali al-'Amr, the Age's honor and its Leader (the Twelfth Imam), may God hasten his appearance. Of course, that holy personage does assist the weak and the destitute and answer the call of the helpless." (1)
He has also written:
"My dear, let not Satan and the carnal self-take hold of you and make the matter appear an insurmountable difficulty in your eyes and thus finish you off by making you refrain from tawbah. Do know that it is better to act in this regard even if to a small extent. If the unoffered prayers, fasts and atonements are many, if God's unfulfilled duties are numerous and the people's usurped rights are innumerable, if your sins are abundant and your vices are plenty, do not despair of God's grace and' do not lose hope in His mercy. God Almighty will facilitate your passage if you act to the extent of your capacity and He will show you the path of salvation." (2)