Exegesis:

pros tēn sklērokardian humōn ‘on account of your hardness of heart.’

pros ‘because of,’ ‘with reference to’; ‘in view of’; ‘having regard to’ (Translator’s New Testament).

sklērokardia (16.14) ‘hardness of heart,’ ‘obstinacy,’ ‘stubbornness’: Lagrange is probably right in referring the word to the lack of docility on the part of the Israelites in their relation to God, their unwillingness to accept his will in the matter. Cf. pōrōsis kardias 3.5; pōroō kardia 6.52.

entolēn (cf. 7.8) ‘commandment,’ ‘legislation.’

Translation:

For hardness of heart see 6.52. In this particular phrase, however, the idiom may require a verbal form, e.g. ‘because your hearts are hard’ or ‘since you do have hard hearts.’

Wrote you this commandment must not be taken in the sense of ‘wrote this commandment to you,’ but rather, ‘wrote this commandment for your sake.’

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 .