As for what al-Hasan ibn Mahbub narrated from Abdullah ibn Sinan, who said:
I heard Abu Abdillah عليه السلام, peace be upon him, saying: "The fifth (khums) is only in spoils specifically."
Ali Akbar al-Ghaffari
Tahdhīb al-Aḥkām fī Sharḥ al-Muqniʿah, vol. 4, p. 161