Exegesis:

hotan idēte tauta ginomena ‘when you see things happening’: in the context ‘these things’ refers primarily to the events described in vv. 24-27, but would include also those described in vv. 14-23.

ginōskete ‘you are to know’: probably here an imperative form (in v. 28 the identical form is clearly indicative).

eggus estin ‘it is near’: the majority of English translations have ‘he is near,’ with obvious reference to ‘the Son of man’ in v. 26 (Le Nouveau Testament. Version Synodale actually translates le Fils de l’homme est proche). Others, for example Lagrange, regard the saying as “mysterious and veiled,” in the style of v. 14, and they believe that one should not attempt to supply any definite subject, e.g. que c’est proche (cf. O Novo Testamento de Nosso Senhor Jesus Cristo. Revisdo Autorizada que est próximo; Luther has es ‘it’; Translator’s New Testament ‘it is near’).

epi thurais ‘at the door’: this figure of speech denotes immediate nearness.

Translation:

Though in English the present tense forms see and know are applicable to a future condition, in many languages this type of condition must have special tense forms applicable to such a future event, ‘when you will see…, then you will know….’ This future usage also requires the use of the future in the dependent clause, e.g. ‘that he will be near.’

At the very gates may be quite meaningless in some languages, for it has no possible relationship to a temporal contract. In fact, its use may completely distort the meaning of the passage in such a way as to cause people to think of the Son of man as standing at the gate of the corral or by the roadside. On the other hand, if the subject of ‘is near’ refers to a general event, then the meaning is even more difficult, for ‘happenings’ cannot be spoken of as being ‘at the very gates,’ unless one is to assume that all these apocalyptic happenings are to take place at the gates. Accordingly, in languages in which the metaphor ‘at the very gates’ is going to be inevitably misunderstood, one may employ ‘is come very near indeed’ (Tabasco Chontal).

Quoted with permission from Bratcher, Robert G. and Nida, Eugene A. A Handbook on the Gospel of Mark. (UBS Handbook Series). New York: UBS, 1961. For this and other handbooks for translators see here .