Hadith: No invading group or detachment sets out to fight in the cause of Allah and gets its share of the booty and returns safe and sound, but it has been given two-thirds of its reward in this world. On the other hand, no invading group or detachment returns defeated and injured but it will receive its full reward in the Hereafter

عن عبد الله بن عمرو بن العاص رضي الله عنهما مرفوعاً: «ما من غازيَةٍ أو سَرِيَّةٍ تغزو فَتَغْنَم وَتَسْلَمُ إلا كانوا قد تَعَجَّلُوا ثُلُثَي أُجُورِهِمْ، ومَا من غَازِيَةٍ أَوْ سَرِيَّةٍ تُخْفِقُ وَتُصَابُ إِلاَّ تم أُجُورُهُمْ».
[صحيح] - [رواه مسلم]

‘Abdullāh ibn ‘Amr ibn al-‘Ās (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: “No invading group or detachment sets out to fight in the cause of Allah and gets its share of the booty and returns safe and sound, but it has been given two-thirds of its reward in this world. On the other hand, no invading group or detachment returns defeated and injured but it will receive its full reward in the Hereafter.”
[Authentic hadith] - [Narrated by Muslim]

Explanation

There are two possible interpretations of this Hadīth: First: The reward of any detachment, which fought the enemy and was safe and received its share of the booty, is less than the reward of another detachment that was injured and took no booty. This interpretation is favored by An-Nawawi (may Allah have mercy upon him). Second: The Hadīth is a proof that the war booty is lawful and does not reduce the reward. Simply, part of the reward is received in this world instead of the Hereafter, and both teams shall receive equal rewards. The victorious one, however, receives two thirds of its reward in advance in this world, but their overall reward is equal. In the Hereafter, Allah compensates those who missed the booty with an amount equal to what they missed, and Allah multiplies the reward for whomever He likes. This is the interpretation of Ibn ‘Abd al-Barr (may Allah have mercy upon him).