What is hypocrisy and what is its danger to Muslims?

Hypocrisy is a dangerous disease and a grave sin. It is the outward display of Islam while concealing disbelief, and it is considered more dangerous than disbelief, with a harsher punishment, because Allah has placed the hypocrites in the lowest depths of the Fire. Hypocrites waver between believers and disbelievers. They are the most averse people to the religion of Allah, and their actions revolve around their interests, so they show faith to the believers and disbelief to their devils. Among their characteristics are disbelief in Allah, enmity and envy towards believers, mockery of Allah, His Messenger, and His religion, corruption on earth, slander and lies, enjoining evil and forbidding good, stinginess, covetousness, and greed. Among their characteristics are also: if they speak, they lie; if they covenant, they betray; if they promise, they break it; if they dispute, they act defiantly; and their concern for outward appearance while their inner being is corrupt. Hypocrites are a hidden enemy from within, causing greater harm and posing a more severe danger to Muslims. Allah has decreed that their destiny and the destiny of disbelievers is Hell, and Allah has commanded to strive against them.