The purpose of Islamic morality is to please Allah. Islam is submission to Allah and a Muslim is someone who has submitted to Allah. A Muslim lives his life in a way that pleases Allah. Allah has communicated his wishes via the Quran. Allah’s guidance by which a Muslim should live his life is revealed in the Quran. For a Muslim, being a good person, and living a moral life means following the Quran. The more closely a Muslim follows the Quran, the better a Muslim he is and hence the better he is as a person, according to Islam.
A Muslim can therefore do whatever is permitted in the Quran and do nothing that is forbidden in the Quran. This makes moral decisions very simple.
Actions have consequences. All human actions have some impact on the person undertaking the action, and in many cases on those other than the person undertaking the action. The Quran forbids many things which have negative consequences. For example, drinking is forbidden in Islam and has negative consequences on people’s behaviour and health. Stealing is forbidden and it deprives others of their possessions.
The morality of the Quran, which is the same thing as Allah’s will, appears to be conducive to the benefit of human beings. The rationale appears to be that Allah is wiser than humans in determining what is good for humans and therefore it is better to follow Allah than to device a system of morality based on human understanding.
There are many things which are permitted in the Quran which are harmful to some humans. For example, it is justified for a Muslim to attack a non Muslim society or government and make war upon it regardless of whether that society or government has harmed Muslims. It is also permitted during war to kill captured enemies and to take women from the enemy by force against their own will. It is also justified to plunder the enemy of his goods.
As these things are permitted in the Quran, they are the will of Allah and therefore cannot be questioned by a Muslim. No one has the right to consider whether there is a better morality as this would be to seek to usurp Allah.
In addition, there are many other actions which are simply not discussed in the Quran which, not being forbidden are assumed to be permitted in Islam.
In Buddhism, the purpose of morality is to reduce and ultimately to end, suffering to oneself and to others. Actions as well as words and even thoughts should have the well being of others and oneself as their goal.
In Buddhism it is recognised that all living beings have the capacity to suffer and therefore one should not harm other beings. This includes not only non Buddhists but also non humans. For human compassion should extend to animals too as their capacity to suffer is as great as our own.
Guiding our actions on this principle prevents us from undertaking actions which might cause harm to others. It also will reduce the chance that we will act upon some other agenda, for example personal greed, while conning ourselves into thinking that we are acting in a moral way. It also enables us to guide ourselves through the various situations that arise upon which explicit guidance has not been given or is not available.