Hadith: You will receive seven hundred she-camels in return for it on the Day of Resurrection, all wearing bridles

عن أبي مسعود رضي الله عنه قال: جاء رجل إلى النبي صلى الله عليه وسلم بناقة مَخْطُومَةٍ، فقال: هذه في سبيل الله، فقال رسول الله صلى الله عليه وسلم : «لك بها يوم القيامة سبعمائة ناقة كلها مخطومة».
[صحيح] - [رواه مسلم]

Abu Mas‘ūd (may Allah be pleased with him) reported that a man came to the Prophet (may Allah's peace and blessings be upon him) with a she-camel wearing a bridle and said: "This is (a donation) in the cause of Allah." The Messenger of Allah (may Allah's peace and blessings be upon him) said: "You will receive seven hundred she-camels in return for it on the Day of Resurrection, all wearing bridles."
Sahih/Authentic. - [Muslim]

Explanation

This Hadīth encourages spending in the cause of Allah, especially in matters which contribute to the war effort such as horses, she-camels or the like. Allah multiplies the reward for such spending seven hundred times. In the Qur'an, Allah, the Almighty, says: {The example of those who spend their wealth in the way of Allah is like a seed [of grain] which grows seven spikes; in each spike is a hundred grains. And Allah multiplies [His reward] for whom He wills. And Allah is all-Encompassing and Knowing.} When animals are bridled, this enables their owner to control them better. So, it was kind of that man to give bridled she-camels, and as a result Allah rewarded him with seven hundred she-camels, all of which were bridled.