John Gill Commentary Luke 17:25

"But first must he suffer many things and be rejected of this generation." — Luke 17:25 (ASV)

But first must he suffer many things
By cruel mockings, spitting, buffeting, scourging, and, at last, death itself; all which must be, and were before his day came, or he entered into his glory, or came in it:

and be rejected of this generation ;
as the Messiah, and be treated with the utmost scorn and contempt, and in the most base and ignominious manner: being put to the death of the cross, and hanged upon the accursed tree: all which were necessary, "must" be; on account of the purposes and decrees of God; the covenant engagements of Christ; the predictions of the prophets of the Old Testament, and his own; and the salvation of his people.