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"Pay attention to what I am about to tell you"

I will keep nothing back from you

The phrase "keep nothing back from you" is an idiom that means to tell someone everything. This can be stated in positive form. Alternate translation: "I will tell you everything the Lord tells me" (See: rc://en/ta/man/translate/figs-idiom and rc://en/ta/man/translate/figs-activepassive)