Allah (swt) said: "And be steadfast in prayer and regular in charity" (Holy Qur'an, Chapter 2, verse 110).
Allah (swt) said addressing the messenger of Allah, Mohammad (pbuh): "Of their goods take alms (charity), so that you might purify and sanctify them, and pray on their behalf" (Holy Qur'an, Chapter 9, verse 103).
When the messenger of Allah, Mohammad (pbuh), sent one of his companions to call the people of Yemen to Islam, he asked him to tell them the basics of Islam, among which was: "... and tell them that Allah has made obligatory on them a charity that is taken from their rich and given to their poor..." (Reported by Bukhari and Muslim).
Allah (swt) said: "So he who gives (in charity) and fears (Allah), and (in all sincerity) testifies to the Best, We will indeed make smooth for him the path to Bliss. But he who is a greedy miser and thinks himself self-sufficient, And gives the lie to the Best, We will indeed make smooth for him the Path to Misery; Nor will his wealth profit him when he falls headlong (into the hell fire)." (Holy Qur'an, Chapter 92, verses 5-11).
Allah (swt) said: "By no means shall you attain righteousness unless ye give (freely) of that which you love; and whatever you give, Allah knows it well." (Holy Qur'an, Chapter 3, verse 92).
Allah (swt) said: "O ye who believe! Cancel not your charity by reminders of your generosity or by injury, like those who spend their substance to be seen of men, but believe neither in Allah nor in the Last Day. They are in Parable like a hard barren rock, on which is a little soil; on it falls heavy rain, which leaves it (just) a bare stone. They will be able to do nothing with aught they have earned. And Allah guideth not those who reject Faith." (Holy Qur'an, Chapter 2, verse 264).