Jamieson, Fausset and Brown on Mark 13:30

30. Verily I say unto you, that this generation shall not pass fill all these things be done--or "fulfilled" (Mt 24:34; Lu 21:32). Whether we take this to mean that the whole would be fulfilled within the limits of the generation then current, or, according to a usual way of speaking, that the generation then existing would not pass away without seeing a begun fulfilment of this prediction, the facts entirely correspond. For either the whole was fulfilled in the destruction accomplished by Titus, as many think; or, if we stretch it out, according to others, till the thorough dispersion of the Jews a little later, under Adrian, every requirement of our Lord's words seems to be met.