be enough for me to perform ghusl after major impurity.

Jābir replied, “It sufficed one who had more and thicker hair than you, and who is better than you—meaning the Messenger of Allah ﷺ—so he was certainly more concerned than you are about his purity and his religion.”

After washing himself with that single sāʿ, he then led us in prayer, which proves that he achieved complete purification with that amount.

Points derived from the ḥadith
1- The obligation of ghusl in the state of major impurity is fulfilled by pouring water over the body so that it flows across the limbs; once this occurs, the duty has been discharged.
2- As stated in Bidāyat al-Mujtahid, the narration provides no conclusive evidence either for the requirement of rubbing the body (dalk) during ghusl or for its non-requirement.
3- A sāʿ—equivalent to four mudd—is sufficient for ghusl after major impurity. Ibn Daqīq al-ʿĪd noted that this figure is not intended as an absolute limit, for various ḥadiths mention differing quantities, which—Allah knows best—may reflect changing circumstances: scarcity or abundance of water, travel or residence, and so forth.
4- It is recommended to be economical with the water used for purification.
5- One should censure anyone who departs from the practice (sunnah) of the Prophet ﷺ.