Source of statement that unqualified Jihad means Jihad by the sword?

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.