What is the meaning of Imam Hussein's saying: "Behold, the illegitimate son of the illegitimate father has focused on two things: the sword or humiliation – and far be it from us to accept humiliation," and who is meant by "the illegitimate son of the illegitimate father"?

This saying is not mentioned in the books of Ahl al-Sunnah wal-Jama'ah. Rather, it is cited by some people of innovation, who interpret "the claimant, son of the claimant" as referring to Ubayd Allah ibn Ziyad, the Amir of Iraq who prepared the detachment that killed Al-Husayn ibn Ali, may Allah be pleased with them both. "At the sillah" means at the drawing of swords. Thus, the meaning is that Ubayd Allah ibn Ziyad presented Al-Husayn and those with him with two options: either fight or be humiliated.