Praise be to Allaah.
What is prescribed for the Muslim in Ramadaan and at other times is to strive hard against his self that is inclined towards evil, so that it will become at peace and inclined towards good. He must strive against the enemy of Allaah, Iblees, so that he will be safe from his evil and his traps. In this world the Muslim is engaged in a mighty, ongoing struggle against himself, his whims and desires, and the shaytaan. He must repent a great deal and pray for forgiveness at all times, but times vary one from another.
The month of Ramadaan is the best month of the year, for it is a month of forgiveness, mercy and ransom from Hell. If the month is good and the place is good, then good deeds will be multiplied and the sin incurred by bad deeds will be greater. Sin in Ramadaan is worse than sin at any other time, just as an act of worship in Ramadaan brings a greater reward from Allaah than an act of worship at any other time. As Ramadaan has such a high status, worship at that time is of great virtue and is multiplied greatly, and the sin at that time is worse than sin at any other time.
The Muslim must make the most of this blessed month by doing righteous deeds and giving up evil deeds, so that Allaah may bless him with acceptance and help him to remain steadfast in adhering to the truth. But bad deeds always remain the same and are not multiplied in number either in Ramadaan or at other times.
As for good deeds, they are multiplied by ten times or more, because Allaah says in Soorat al-An’aam (interpretation of the meaning): “Whoever brings a good deed (Islamic Monotheism and deeds of obedience to Allaah and His Messenger صلى الله عليه وسلم) shall have ten times the like thereof to his credit, and whoever brings an evil deed (polytheism, disbelief, hypocrisy, and deeds of disobedience to Allaah and His Messenger صلى الله عليه وسلم) shall have only the recompense of the like thereof, and they will not be wronged” [al-An’aam 6:160]. And there are many similar verses.
Similarly, in special places such as the two Holy Sanctuaries (in Makkah and Madeenah), good deeds are greatly multiplied in terms of quantity and degree, but bad deeds are not multiplied in terms of quantity, but they may be more serious at a special time and in a special place, as indicated above.
Majmoo’ Fataawa al-Shaykh Ibn Baaz (15/446).