Exodus 20:20 New English Translation

²⁰Moses said to the people, “Do not fear, for God has come to test you,^[a] that the fear of him^[b] may be before you so that you do not^[c] sin.”

Exodus 20:20 tn נַסּוֹת (nassot) is the Piel infinitive construct; it forms the purpose of God’s coming with all the accompanying phenomena. The verb can mean “to try, test, prove.” The sense of “prove” fits this context best because the terrifying phenomena were intended to put the fear of God in their hearts so that they would obey. In other words, God was inspiring them to obey, not simply testing to see if they would.
Exodus 20:20 tn The suffix on the noun is an objective genitive, referring to the fear that the people would have of God (GKC 439 §135.m).
Exodus 20:20 tn The negative form לְבִלְתִּי (l^evilti) is used here with the imperfect tense (see for other examples GKC 483 §152.x). This gives the imperfect the nuance of a final imperfect: that you might not sin. Others: to keep you from sin.

New English Translation (NET)