Exegesis:

ho ouranos kai hē gē ‘heaven and earth,’ ‘the whole created universe.’

hoi … logoi mou ‘my words’: although in the context this refers to the discourse, it is better literally to translate ‘my words,’ ‘my teachings’ (cf. hoi emoi logoi ‘my words’ in 8.38).

Translation:

Heaven in this context is to be understood as the ‘sky,’ not the abode of God. Hence, one may translate ‘the sky and the earth will come to an end’ (Tzeltal, Copainalá Zoque), or ‘the sky and the earth will exist no more.’

Some translators have interpreted this verse as ‘even though the sky and the earth should pass away, my words would not pass away,’ but though this may be implied, it is not a necessary or recommended rendering.

Depending upon the expression used in the first clause, one may translate the second clause as ‘my words will not come to an end’ or ‘my words will not cease to exist.’ On the other hand, the mere continuation of words may not clearly indicate the meaning of this passage, which denotes the fact that the statements of Jesus will have eternal validity. Accordingly, in some languages one must translate as ‘my words will always have their power’ or ‘my words will never stop being strong’ (in the sense of true, dependable prophecy).

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 .