ALLAH is ever merciful & compassionate....
WHO gave ANY MORTAL the right to kill anyone?
Even if Divinely sent & guided prophets words were misinterpreted or taken out of context by sinful mortal men, NONE of the monotheist faith will discount that the 10 Commandments was the ONLY book that ALLAH had written.
Before anyone who picks up a stone to KILL anyone, do consider the Commandments carefully:-
-Thou shalt not kill
-Thou shalt not bear false witness against thy neighbor
-Thou shalt not steal
-and MOST CRITICALLY - Thou shalt not take the name of the LORD, thy GOD, in vain.
So, who is only a mere mortal, attempting to act as the DIVINE & on HIS behalf?
ALLAH, who is ever merciful & compassionate, is also wise.
Adultery is harmful, as it does not hurt only one or two, but ENTIRE families - RELATIONSHIPS of the beloved & loved ones, relatives & friends on BOTH sides which may even lead to harmful & hurtful actions to each other. Thus the need for such a Commandment as families are the Building Blocks of Civilization. However, no where did ALLAH said to kill them, & worse if based upon false witness testimonials.
"Vengence is MINE, says the Lord". Divine Retribution is REAL & will come in many ways, unrecognizable initially, but the dawning comes eventually & thus regrets which is already too late.....
Thus all we mere flawed mortal Humans can do in order to enforce that Commandment is thru legislative societal law, - DETERRENCES - to protect the innocent & punished the perpetrators whom broke that Commandment - male or female or both, & leave the rest for our Almighty, who created us, knows each & everyone's deepest darkest secrets & motivations.... to decide.