Is the intention (Niyyah) obligatory for Ghusl?
Chapter on Ghusl from Janabah (Major Impurity)
Al-Mughni
Book of Purification
Primary text
The intention is obligatory for Ghusl. This is established because Umm Salamah asked the Prophet (PBUH) specifically concerning the Ghusl for major ritual impurity (Janaabah), and the washing for Janaabah cannot be valid except with the intention.