Exegesis:

ti me legeis agathon lit. ‘what do you call me good?’ Interrogative ti may inquire after the cause and be rendered ‘why’ or express astonishment at what has been said or done and mean, ‘what!,’ i.e. ‘how could you,’ preferably the latter.

oudeis agathos ei mē heis ho theos ‘no one is good except one, i.e. God.’

Translation:

Call me good may have to be rendered ‘say that I am good’ (Sranan Tongo, where a more literal rendering would cause ‘good’ to be taken as a name or title).

No one is good but God alone, or, ‘(only) God is good, no one else (is good)’; or, in order to avoid classifying God as a human being, ‘not any man is good, only God is (good).’

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.