Sheath, also known as Seth, was the son of Adam and Hawwa (Eve) and a prophet and messenger of Allah. His name means "gift," as he was given to Adam and Hawwa as a replacement for their deceased son, Habil (Abel). Habil was killed by his brother Qabil (Cain) out of jealousy and resentment. Allah warned Qabil not to let his jealousy consume him, but he refused to listen and committed the first murder in human history.
Sheath was a righteous man who obeyed Allah's commands and taught them to his brothers, nephews, and other descendants of Adam. After Adam's death, Sheath ruled over the children of Adam with justice and brought unity among them.
However, Shaitan (Satan) continued to plot against Sheath and his people. One of Sheath's nephews, Qabil (Cain), was known for his aggression, greed, and arrogance. He decided to leave the others and go off on his own. Sheath, following Allah's instructions, avoided mixing with Qabil and his descendants.
In order to continue misguiding Qabil and his people, Shaitan disguised himself as a young apprentice and worked for a blacksmith. He designed a flute and other musical instruments, which attracted Qabil and his people. They became so engrossed in the music and continued to become more distant from Allah's commands. This lead to free-mixing between genders and eventually adultery and fornication. Sheath continued to remind them of their duties as Muslims, but Shaitan continued to lead them astray.
The descendants of Sheath and Qabil remained separate, with Sheath's descendants following the teachings of Allah and Qabil's descendants falling into disobedience and corruption.