50 Grk “Truly (ἀμήν, amēn), I say to you.”
51 This is one of the hardest verses in the gospels to interpret. Various views exist for what generation means. (1) Some take it as meaning “race” and thus as an assurance that the Jewish race (nation) will not pass away. But it is very questionable that the Greek term γενεά (genea) can have this meaning. Two other options are possible. (2) Generation might mean “this type of generation” and refer to the generation of wicked humanity. Then the point is that humanity will not perish, because God will redeem it. Or (3) generation may refer to “the generation that sees the signs of the end” (v. 30), who will also see the end itself. In other words, once the movement to the return of Christ starts, all the events connected with it happen very quickly, in rapid succession.

In other versions

Truly, I say to you, this generation will not pass away until all these things take place.

Truly I tell you, this generation will certainly not pass away until all these things have happened.

Truly I tell you, this generation will certainly not pass away until all these things take place.

I tell you the truth, this generation will not pass from the scene until all these things take place.

Truly I say to you that this generation will never pass away until all these things take place!

Verily I say unto you, This generation shall not pass, till all these things be fulfilled.

Public Domain