"O Prophet, incite the believers to fight" (Qur'an 8:65), meaning: urge them to fight by means of what Allah has promised the martyrs and the striving mujahidin.
Muhammad said: Incitement (tahrid) in the language means for a person to urge another toward a matter until it is known from him that he is 'harid' (one near death/ruin) if he holds back from it. And the 'harid' is one who has approached destruction.
"If there are among you twenty steadfast" (Qur'an 8:65) until His saying: "And Allah is with the steadfast" (Qur'an 8:66).
Al-Hasan said: Allah had obligated the Muslims in this verse to be steadfast against ten.