Military campaigning: is it obligatory?

Ma'mar says: Once Makhul faced the qiblah and swore an oath ten times, then said: Jihad is obligatory upon you. After that he said: If you wish, I can swear even more than this.

Dawud (may Allah have mercy on him) says: I said to Sa'id bin al-Musayyib (may Allah have mercy on him): I know that jihad is obligatory upon all people. Hearing this, he remained silent. I knew that if he disagreed with what I said, he would certainly have made it clear. Then I said to Sa'id bin al-Musayyib (may Allah have mercy on him): I prepared myself for jihad, with nothing driving me but that, until I did frontier duty (ribat). (Is that enough?) He said: It has sufficed for you.

Abdullah bin al-Mubarak (may Allah have mercy on him) says: I asked Ata: Is jihad obligatory? He and Amr bin Dinar said: We do not know.

Sayyiduna Umar (may Allah be pleased with him) says: The foundation of faith is four things: prayer, zakah, jihad and trustworthiness (amanah).

Sayyiduna Hudhayfah (may Allah be pleased with him) says: Islam has eight shares: prayer is a share, zakah is a share, jihad is a share, Hajj is a share, the fast of Ramadan is a share, enjoining what is good is a share, and forbidding what is evil is a share. Whoever has no share has failed.

Sayyidah Aishah (may Allah be pleased with her) says: If any of you senses cowardice in himself, he must never go out on jihad.

Yazid bin Bishr al-Saksaki (may Allah have mercy on him) says: I came to Madinah and visited Sayyiduna Abdullah bin Umar (may Allah be pleased with him). At that time a man from Iraq came to him and said: O Abdullah bin Umar! What is the matter, that you perform Hajj and Umrah but have abandoned jihad in the way of Allah? Sayyiduna Ibn Umar (may Allah be pleased with him) said: Woe to you! Faith is built upon five things: that you worship Allah, establish the prayer, pay zakah, perform Hajj and fast in Ramadan. He repeated it to me and said: O servant of Allah! Worship Allah, establish the prayer, pay zakah, perform Hajj and fast in Ramadan. This is how the Messenger of Allah (peace and blessings be upon him) told us; after these, jihad is a good deed.

Nafi' says: Sayyiduna Ibn Umar (may Allah be pleased with him) used to send his sons out on jihad and mount them on riding animals. Sayyiduna Ibn Umar (may Allah be pleased with him) held that, after prayer, the most excellent deed is jihad in the way of Allah.

Umayyah al-Shami says: Makhul and Raja' bin Haywah used to stay in the rear of the army and would not leave it.

Al-Sha'bi says: The one who prevails in the way of Allah is better than the martyr.