NET

39 David strapped on his sword over his fighting attire and tried to walk around, but he was not used to them. David said to Saul, “I can’t walk in these things, for I’m not used to them.” So David removed them.

Darby

39 And David girded his sword upon his dress, and endeavoured to go; for he had not yet tried [it]. And David said to Saul, I cannot go in these; for I have never tried [them]. And David put them off him.

KJV

39 And David girded his sword upon his armour, and he assayed to go; for he had not proved [it]. And David said unto Saul, I cannot go with these; for I have not proved [them]. And David put them off him.