I am 13 years old. Is it permissible for me to greet my maternal aunt's husband with "peace be upon him"?

The age of thirteen is close to puberty, and at this age, a girl reaches the stage of being desired. She must cover her awrah (private parts), and therefore, it is not permissible for her to shake hands with non-mahram men, including her maternal aunt's husband. This is because shaking hands takes the ruling of touching, and touching a woman who has reached the age of being desired is forbidden.

As for a young girl who is not desired, it is permissible to shake her hand as long as the element of desire is absent.

The different schools of Islamic jurisprudence agree that if a young boy or girl has not reached the age of being desired, it is permissible to touch and shake their hands. However, they differ on specifying this age.