I think it is agreed, that it is always more meritorious to obey a
commandment than to voluntarily perform that which was not cammanded. (in
the words of the Talmud [bava kama 87] 'greater is he who was commanded and
does, than he who was not commanded, and does'- gadol hametzuveh etc...).
The question is, whether a person not commanded should nevertheless go
ahead and do the action, and both the patriarchs, and women, are credited
for doing these actions. According to the Ashkenazi custom, women also may
pronounce a blessing on a mitzvah they were exempt from (sepharadim disagree).
As a matter of fact, the question is asked, if Avraham knew prophetically
what G-d would command the Jewish people, why had he not circumcised
himself already? and the answer given is that, since this commandment,
contrary to all others, *would* be commanded to him, he waited, in order to
be able to do it *better* by being commanded.
I hope this helps clear up your feelings on this matter,
Jerusalem, Israel mailto:email@example.com
http://www.randomc.com/~shimon/ IBMMAIL: I1060211