Reward for women wearing Tzizit

Question

There is a general rule that a person who is not obligated cannot do a mitzvah on behalf of someone who is obligated, and according to at least one Rishon this is because a person who is obligated has a stronger Yetzer Hara, and the more difficulty someone has with a Mitzvah the more reward they get.

Since the person not obligated receives less reward, they cannot do it on behalf of someone who's baseline mitzvah receives more.

But what about Tzizit?

A person is not obligated to wear Tzizit unless he wears a four-cornered garment. Therefore he's not Chayiv in the mitzvah until he puts on the four-cornered garment. A person doesn't have the Yetzer Hara to take off the Tzizit from the garment.

So would women, who are not obligated in Tzizit, receive the same amount of reward as men, who are obligated? In this case, since the level of difficulty is the same, wouldn’t the reward be the same?

(I'm not asking if they can put on Tzizit for men just whether it makes sense that the reward level should be the same)

Answer 1

There are a few misconceptions in your question.

Firstly, it is true that it is considered more worthy for someone obligated to do a mitzva than for someone who isn't obligated. But there is an unrelated, separate principle that

Whoever is not obligated to do a certain matter cannot discharge the obligation on behalf of the community.

(Rosh Hashana 29b)

Secondly, a mitzva that has to be done with the body (חובת הגוף), can only be done by the person themself. The concept of agency (שליחות) doesn't help. (For example, I can appoint an agent to marry a woman for me, but not to do circumcision on my behalf...)

Finally, while it's true that the mitzva of tzitizit is optional since one doesn't have to wear a four-cornered garment, if a man and a woman both wear one, the former is obligated in tzitzit while the latter is not. So the level of obligation is not equivalent.

Hope this helps!