Safeguarding one's and others' lives is among the great divine practices and is considered a Muslim's duty.
Every Muslim must in addition to safeguarding his life, defend another man's life when subjected to assault, particularly if that man is one of the oppressed and weak ones.
It is the duty of societies and governments to ensure and guarantee the right to life for all the people. Not only must they safeguard this right but also defend their citizens before any violation upon men's lives. And it is not allowed to kill anybody without a legal permit.1
Safeguarding the continuation of mankind's life, as far as God has destined, is a legal duty.2
The reason why Islamic law holds the life of one person equal to that of entire mankind,3 is that safeguarding the life of a man and continuation of birth generations depend on safeguarding the life of each individual. Obviously each individual has the responsibility to protect his own life first, as a priority.
In addition to the sanctity of man's blood other qualities and factors which define a man's character are equally respected and considered by Islam.
The sanctity of a Muslim's property and reputation in Islam is as important as his life. Actually because human dignity is the same as the reality of humanity which distinguishes mankind from other creatures.
In the Islamic legal system right to life is not just a right for man, but since a life is a divine bestowment, it creates the right to enjoy this gift for a man. On the other hand it makes him responsible to provide necessary means to safeguard this right and also to keep under consideration (health, feeding, etc) as the essential means that makes this right last.
Thus, the right to life is a divine trusteeship entrusted into the human hands and he must shoulder the responsibility of safeguarding it. That is why it is forbidden for a man to commit suicide (deprive oneself of life) or to damage his body or spirit.