Rashi on Genesis 19:18/רש"י על בראשית י״ט:י״ח

1אל נא אדני OH NOT SO, MY LORD — Our Rabbis said, that this name (Lord) is holy (i. e. refers to God; Shevuot 35b), since it is said regarding him (i.e. regarding the one who was addressed by this name) (v. 19) “[and thou hast magnified thy mercy …] in keeping alive my soul”. Therefore it must refer to Him who has the power to kill or keep alive. Indeed the Targum renders it, “I beg of thee, O Lord)”

2אל נא OH NOT SO — do not tell me to escape to the mountain.

3נא — This word is used when a request is being made.