Allah says in the Holy Qur'an, Sura Al-Baqarah, Ayat 34:
"And when we said to the angels "Prostrate (do Sajdah) to Adam!" they all prostrated save Iblees. He refused and he was rude with pride, and so he became one of the unbelievers."
Iblees was a Jinn who had been taken up to the heavens because he was so good, but when Allah made Adam and told all in heaven to do Sajdah to Adam, Iblees refused. He said he was better than Adam as he had been made from fire and Adam was made from clay.
Iblees had disobeyed Allah because of his pride and because of this not only was he thrown out of Heaven but he will go to Hell and burn there for ever.
What is Pride?
It is something that makes a person think highly of themselves. When someone thinks highly of themselves they consider others below them. They forget their own faults and are not thankful for Allah's blessings.
To cure oneself of pride you should think of Allah and realise that He alone is the All Powerful Creator, deserving of praise and worship.
Our Holy Prophet (S) has said that Allah says, "Greatness is My special right, and whoever tries to share it with Me (becomes proud) I will put him in Hell."
If ever you feel yourself becoming proud, think of yourself at the beginning, when you were born - a little baby, unable to do anything for himself, then think of yourself at the end - in a grave.
We are nothing compared to Allah so we have no right to feel pride. Only He can.
Humility / Humbleness:
This means to be AWARE of one's status according to Islam. The opposite of humility is arrogance / pride. This means to think of yourself as better than others. This was Iblees's mistake and it is why he is cursed.
In Islam we are told that no one is better than another. So, humility means to know that we are no better than anyone else, and that is how we should behave. The greatest enemy of humility is our NAFS. Whenever we do anything good, it tells us that we've done something good and how great we are. This means that YOU must protect YOURSELF against getting "big headed."
Our 4th Imam (A) says in Sahifa e Kamila:
"O Lord, do not honour me even one degree among the people unless You lower me to an equal amount in my own soul.
Create for me no outward respect unless You have created for me an equal amount of HUMILIATION in my spirit."
WHAT IS A HUMBLE PERSON LIKE? DOES HE GO AROUND DOING TASBEEH ALL DAY?
NO, he does not. The sign of a humble person can be explained by the words of Imam Ali (A)
"From the signs of humility is to be content with any place in an assembly, to salute when you meet, to abandon quarrels and discord even if you were on the right; and not to except (love) praise for your fear of Allah."
A person who is humble is said to have modesty. That means he does not go around telling everybody how great he is. Nor does he become proud when others praise him.
Why should we be humble?
By being humble, we are showing to the world that Allah has created all men equal, whether they are black, brown, white or yellow.
We are showing that the only person who is greater in the eyes of Allah is the person who has Taqwa (ashamed of displeasing Allah).
Our Holy Prophet (S) has said: "Pride enters the heart like a black ant crawling over a black rock at night."
This shows how easily pride can overtake us, and also shows the importance of being humble so as to protect yourself against pride.
In the Du'a after Asr prayers we say to Allah:
"My Lord , whatever talents I have got, it is but from You."
If we want to remain humble, we should always remember this sentence and say it to ourselves EVERY time we do something good, or come first or win something. That way we will stop our nafs from praising us, and make it praise Allah.
The Holy Prophet (S) has said: "Indeed, humility exalts a man's position with Allah. Thus be humble and Allah will shower you with mercy."