The Messenger of Allah ﷺ used to grant additional shares of the spoils to certain members of the expeditions he dispatched, set aside specifically for them beyond the general distribution given to the rest of the army, and the fifth was obligatory in all of that.
حدثنا عبد الملك بن شعيب بن الليث قال حدثني أبي عن جدي ح و حدثنا حجاج بن أبي يعقوب قال حدثني حجين قال حدثنا الليث عن عقيل عن ابن شهاب عن سالم
أن رسول الله ﷺ قد كان ينفل بعض من يبعث من السرايا لأنفسهم خاصة النفل سوى قسم عامة الجيش والخمس في ذلك واجب كله
Narrated by Muslim in the book of jihad and campaigns, chapter on spoils, hadith no. 40/1750, from Abdul-Malik bin... etc., Shuayb, and Bukhari in the book of the obligation of khumus, chapter on evidence that khumus is for the pressing needs of the Muslims, hadith no. 3135, from the hadith of Layth bin Saad, with the same wording.