According to Exodus 2, the infant Moses was hidden by his mother for three months.
The biblical account says Moses’s mother concealed him after Pharaoh ordered that newborn Hebrew boys be cast into the Nile. When she could hide him no longer, she placed him in a basket made of papyrus and set it among the reeds along the riverbank.
Moses’s sister watched from a distance. Pharaoh’s daughter found the basket and adopted the child, while Moses’s own mother was employed to nurse him. This episode begins the story of Moses’s rescue and eventual role in leading the Israelites out of Egypt.
The three-month period belongs specifically to Moses’s infancy. It should not be confused with the later periods of forty days associated with Moses on Mount Sinai or the forty years associated with Israel’s wilderness journey.