I was reading an article in a magazine which quoted a rule from Ibn Hajar Al-Asqalani, roughly translated it says:
In the Kitab and Sunnah whenever the word jihad is used without a restriction added on to it, such as with wealth or with life, the salaf are fully in agreement that it means war with the sword.
I would like a reference (original book etc. by Ibn Hajar) for this if someone can find it.
I couldn't source the exact quote you mentioned, though as a comment mentions, I've read this elsewhere.
In Fath al-Bari, a commentary on Sahih al-Bukhari, ibn Hajar describes jihad as toiling, labouring, facing hardship, and difficulty. In the Shariah, it means exerting and struggling against the infidels. It is also used in the sense of a struggle against the devil (Shaytan) to reject his insinuations.
Imam Bukhari's Book of Jihad and Sair has various ahadith extolling the different kinds of jihad and the rewards of different categories of mujahideen. Many of these relate to martyrdom, chivalry in the battlefield, mobilisation for jihad, and the mujahideen's desire to return to the world to fight in Allah's cause once again.
Many of these ahadith use the phrase الْجِهَادُ فِي سَبِيلِ اللَّهِ (striving in the cause of Allah), or just the unqualified جِهَادٌ or الْجِهَادَ to refer to an armed struggle, so even though I couldn't find an exact citation for the quote, it seems to be an understanding of the word that isn't generally in error.
