Once a person asked Imam Hasan (a.s), what was the distinguishing feature of a eunuch. He said, “Regarding whom it is not known whether it is a man or a woman, but he is having both the sex organs. Then one should wait till his maturity. If he has ejaculation of semen, he is a man and if has menses and the breasts become prominent, it is a woman. And if this also does not establish the sex, then while urinating if the urine spouts in a straight line it is a man and if it drops like urine of she-camels it is a woman.”
This man further asked, “What are those ten things, that are harder than each other?” Imam (a.s) said, “Allah has made stone hard and made iron harder than it; because it breaks the stone and fire is stronger than iron because it melts the iron and water is more powerful than fire because it extinguishes the fire and the cloud is more powerful because it has control over water; and wind is more powerful than the cloud because it moves the cloud and more powerful than wind is the angel who controls it and more powerful than this angel is the angel of death who would capture his soul. And death is more powerful than the angel of death that he himself would be subjected to death. More powerful than death is the command of God Almighty, as by this death arrives and is warded off.”
Reference :Akhlaq al-A’imma, Morals & Manners of the Holy Imams