The intended meaning of the great sacrifice is Imam Husain (a.s.)

مراد به ذبح عظيم، حسين است

آيه‌ي هشتم: (و فديناه بذبح عظيم): [1071] در خبر است كه مراد به ذبح عظيم حسين (عليه‌السلام) است. [1072] .و وارد نيايد اينكه مفدي بايد اعظم از فدا باشد، زيرا كه باء سببيه است نه تفديه، و معني آن است كه: ما فدا نموديم او را به آنچه فدا نموديم به سبب ذبح عظيمي كه مقدر بوده در صلب او، يا اينكه مراد اين باشد كه مبدل شد فدا شدن او در راه خدا به فدائي بزرگتر از او، و اين مرتبه‌ي عظمي كه فداي راه خدا شدن باشد از براي حسين (عليه‌السلام) حاصل شد.

The intended meaning of the great sacrifice is Imam Husain (a.s.).

Verse eight: (and We ransomed him with a great sacrifice): [1071]

It is reported that the great sacrifice refers to Imam Husain (a.s.) (peace be upon him). [1072]

And it should not be assumed that the one who is ransomed must be greater than the ransom, because the “bi” here is a preposition of cause, not of substitution, and its meaning is:

We ransomed him with that which we ransomed him because of the great sacrifice that was decreed in his loins, or it may mean that his being ransomed in the path of God was transformed into a sacrifice greater than him, and this supreme rank of being sacrificed in the path of God was attained by Imam Husain (a.s.) (peace be upon him).