Hadith: The example of a Mujāhid in the cause of Allah is like a person who keeps fasting, praying and reciting the verses of Allah unfailingly until the Mujāhid returns

عن أبي هريرة رضي الله عنه قال: قيل: يا رسول الله، ما يعدل الجهاد في سبيل الله؟ قال: «لا تستطيعونه» فأعادوا عليه مرتين أو ثلاثًا كل ذلك يقول: «لا تستطيعونه»! ثم قال: «مثل المجاهد في سبيل الله كمثل الصائم القائم القانت بآيات الله لا يَفْتُرُ من صيام، ولا صلاة، حتى يرجع المجاهد في سبيل الله». وفي رواية البخاري: أن رجلاً قال: يا رسول الله، دلني على عمل يعْدِلُ الجهاد؟ قال: «لا أجده» ثم قال: «هل تستطيع إذا خرج المجاهد أن تدخل مسجدك فتقوم ولا تفتر، وتصوم ولا تفطر»؟ فقال: «ومن يستطيع ذلك؟!»
[صحيح] - [متفق عليه، والرواية الثانية للبخاري]

Abu Hurayrah (may Allah be pleased with him) narrated that the Messenger of Allah (may Allah's peace and blessings be upon him) was asked: "O Messenger of Allah, what is equivalent to Jihad in the cause of Allah?” He answered: “You can not do it.” The question was repeated twice or thrice to which he gave the same answer. Then he said: “The example of a Mujāhid in the cause of Allah is like a person who keeps fasting, praying and reciting the verses of Allah unfailingly until the Mujāhid returns.” In the version narrated by Al-Bukhāri: A man said: "O Messenger of Allah, show me a deed that equals Jihad.” The Prophet replied: "I do not find one." Then he said: "When the Mujāhid goes out for Jihad, can you enter your place of prayer and pray incessantly and fast without breaking your fast?" The man replied: "Who can do that!"
[Authentic hadith] - [Narrated by Bukhari - Narrated by Bukhari & Muslim]

Explanation

In both narrations of this Hadīth, the Companions asked the Prophet (may Allah's peace and blessings be upon him) about the deeds that would yield the same reward of going out for Jihad in the cause of Allah. He replied: “You cannot bear it.” He meant that they could not do the deeds that would equal Jihad. When they repeated the question twice or thrice, he kept telling them that they are unable to do it. Then, he clarified to them that the only thing that would equal the reward of Jihad is that they keep performing prayers day and night and reciting the Qur'an continually, which is undoubtedly beyond the ability of humans. In the version narrated by Al-Bukhāri, a man from the Companions of the Prophet (may Allah's peace and blessings be upon him) asked him to guide him to a deed that would equal the prestigious status of Jihad and the grand reward it entails, to which the Prophet replied: “I do not find one.” He meant that he could not find any deed that had the same merit of Jihad. Another Hadīth narrated by Al-Bukhāri and Muslim confirms this meaning: “Verily, setting out in the early morning or evening for the sake of Allah is better than this whole world with all its pleasures.” Then, the Prophet (may Allah's peace and blessings be upon him) asked the man the following question: When the Mujāhid goes out for Jihad, can you go into your place of prayer and remain therein pray incessantly along with fasting without breaking your fast? If you can do this, then this is the only thing that is equivalent to Jihad (in reward). At that point, the man said: “Who can do that?” He meant that it is undoubtedly beyond the human ability to keep praying without stopping and fasting without eating.