Fasad means spreading corruption and mischief in the land. Islam is a religion which promotes peace and solidarity among everyone and it severely seeks to prevent corruption and evil in the land.
فَسَاد ( اسم ) : اِنْحِلال
corruption ; decay ; decomposition ; degeneration ; disintegration ; putrefaction ; putridity ; rot 
There are numerous aayaath in the Quran about not spreading corruption. Some of them are:
Man is very forgetful and makes a lot of mistakes. His own self (nafs) tells him to do evil and the Shaytaan tempts him to commit sin. When bodies get sick and are afflicted with disease, one has to find a doctor who can prescribe the appropriate medicine so that the body may be restored to full health. Similarly, souls and hearts may be afflicted with the diseases of desire and doubt, so people do things which Allaah has forbidden, such as shedding blood, committing adultery, drinking alcohol, oppressing people and consuming their wealth unlawfully, preventing people from following the way of Allaah and disbelieving in Allaah.
The diseases of the heart [psychological and spiritual diseases] are worse than diseases of the body. This means that one must find a doctor who is skilled in treating such diseases. Because the diseases of the heart are so many and cause the spread of evil and corruption, Allaah has enjoined the believers to treat these diseases, by enjoining that which is good and forbidding that which is evil. Allaah says (interpretation of the meaning): “Let there arise out of you a group of people inviting to all that is good (Islam), enjoining Al-Ma‘roof (i.e. Islamic Monotheism and all that Islam orders one to do) and forbidding Al-Munkar (polytheism and disbelief and all that Islam has forbidden). And it is they who are the successful” Surah Aal ‘Imraan 3:104
Enjoining what is good (al-ma’roof) and forbidding what is evil (al-munkar) is one of the most important Islamic duties, indeed it is the noblest and most sublime. This is the task of the Prophets and Messengers (peace be upon them all), as Allaah says (interpretation of the meaning): “Messengers as bearers of good news as well as of warning in order that mankind should have no plea against Allaah after the (coming of) Messengers” Surah al-Nisa’ 4:165
Allaah has made the Muslim ummah the best nation ever raised up for mankind, in order to do this important task, as Allaah says (interpretation of the meaning): “You (true believers in Islamic Monotheism, and real followers of Prophet Muhammad and his Sunnah) are the best of peoples ever raised up for mankind; you enjoin Al-Ma‘roof (i.e. Islamic Monotheism and all that Islam has ordained) and forbid Al-Munkar (polytheism, disbelief and all that Islam has forbidden), and you believe in Allaah” Surah Aal ‘Imran 3:110
If the ummah fails to do its duty of enjoining what is good and forbidding what is evil, wrongdoing and corruption will spread throughout the ummah, and it will deserve the curse of Allaah. For Allaah cursed those among the Children of Israel who disbelieved because they failed in this important duty. Allaah says (interpretation of the meaning): “Those among the Children of Israel who disbelieved were cursed by the tongue of Dawood (David) and ‘Eesa (Jesus), son of Maryam (Mary). That was because they disobeyed (Allaah and the Messengers) and were ever transgressing beyond bounds.
They used not to forbid one another from Al-Munkar (wrong, evildoing, sins, polytheism, disbelief) which they committed. Vile indeed was what they used to do Surah al-Maa’idah 5:78
Enjoining what is good and forbidding what is evil is one of the basic principles of this religion, and doing this is striving for the sake of Allaah. Striving requires putting up with difficulties and bearing insults and harm with patience, as Luqmaan said to his son: “O my son! Aqim-is-Salaah (perform As-Salaah), enjoin (on people) Al-Ma‘roof (Islamic Monotheism and all that is good), and forbid (people) from Al-Munkar (i.e. disbelief in the Oneness of Allaah, polytheism of all kinds and all that is evil and bad), and bear with patience whatever befalls you. Verily, these are some of the important commandments (ordered by Allaah with no exemption)” Surah Luqmaan 31:17
Enjoining what is good and forbidding what is evil is an important mission, hence those who undertake this mission must be of good character and must understand the objectives of sharee’ah; they must call people with wisdom and fair preaching and deal with them in a kind and gentle manner, so that Allaah may guide those whom He wills at their hands. Allaah says (interpretation of the meaning): “Invite (mankind, O Muhammad) to the way of your Lord (i.e. Islam) with wisdom (i.e. with the Divine Revelation and the Qur’aan) and fair preaching, and argue with them in a way that is better. Truly, your Lord knows best who has gone astray from His path, and He is the Best Aware of those who are guided” Surah al-Nahl 16:125
The ummah which establishes the symbols of Islam, enjoins what is good and forbids what is evil, will attain happiness in this world and in the Hereafter. Allaah will send them His support and grant them victory, as He says (interpretation of the meaning): “Verily, Allaah will help those who help His (Cause). Truly, Allaah is All-Strong, All-Mighty.Those (Muslim rulers) who, if We give them power in the land, (they) enjoin Iqamaat-as-Salaah [i.e. to perform the five compulsory congregational Salaah (prayers) (the males in mosques)], to pay the Zakaah and they enjoin Al-Ma‘roof (i.e. Islamic Monotheism and all that Islam orders one to do), and forbid Al-Munkar (i.e. disbelief, polytheism and all that Islam has forbidden) [i.e. they make the Qur’aan as the law of their country in all the spheres of life]. And with Allaah rests the end of (all) matters (of creatures)” Surah al-Hajj 22:40-41
Enjoining what is good and forbidding what is evil is a mission which will never end until the Hour begins. It is obligatory upon all the ummah, rulers and subjects, men and women, each according to his or her circumstances. The Prophet ﷺsaid: “Whoever among you sees an evil action, let him change it with his hand [by taking action]; and if he cannot, then with his tongue [by speaking out]; and if he cannot, then with his heart [by feeling that it is wrong] – and that is the weakest of faith.” Sahih Muslim, 49
The Muslim ummah is one nation, and if corruption becomes widespread in it and its circumstances turn bad, then all the Muslims are obliged to reform it, rid it of evil things, enjoin what is good and forbid what is bad, and offer sincere advice to all. The Prophet ﷺsaid: “Religion is sincerity.” We said, “To whom?” He said, “To Allaah and His Book, and His Messenger, and to the leaders of the Muslims and their common folk.” Sahih Muslim, 95.
If a Muslim is commanded to do something, he should be the quickest of people to do it, and if he is forbidden to do something, he must be the one who keeps furthest away from it. Allaah has issued a warning to those who go against that, as He says (interpretation of the meaning):“O you who believe! Why do you say that which you do not do? Most hateful it is with Allaah that you say that which you do not do” Surah al-Saff 61:2-3
No matter how righteous a person may be, he still needs sincere advice, guidance and reminders in the light of the Qur’aan and Sunnah. Allaah said to the Messenger of the Allaah,: “O Prophet (Muhammad)! Keep your duty to Allaah, and obey not the disbelievers and the hypocrites (i.e., do not follow their advice). Verily, Allaah is Ever All-Knower, All-Wise” Surah al-Ahzaab 33:1
So we must all enjoin that which is good and forbid that which is evil, so that we may attain the Pleasure of Allaah and His Paradise.