Sahl bin Mu'adh bin Anas (may Allah have mercy on him) narrates from his father, Sayyiduna Mu'adh bin Anas (may Allah be pleased with him), that a woman came to the Prophet (peace and blessings be upon him) and said: My husband has gone out for jihad in the path of Allah, and when he prayed I used to follow his prayer and follow his deeds. So tell me of a deed that will bring me to his deed until he returns. The Prophet (peace and blessings be upon him) said to her: "Are you able to stand without sitting down, to keep remembering (Allah) without slackening, and to fast without breaking your fast until he returns?" She said: I am not able to do this, O Messenger of Allah. He (peace and blessings be upon him) said: "By the One in whose hand my soul is, even if you did that, you would not reach a tenth of his deed until he returns."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 17575