Should it please my father to do you harm: this awkward wording may be more naturally rendered “if he wants to harm you” (Contemporary English Version) or “if my father intends to do you harm” (New Jewish Publication Society’s Tanakh).

The LORD do so to Jonathan, and more also: since Jonathan is the person who is speaking here, it will be unnatural in most languages to have him refer to himself in the third person as in Hebrew and Revised Standard Version. The pronoun “me” will be much more appropriate. On the curse formula the LORD do so … and more also, see the comments at 3.17, and compare also Ruth 1.17. These words stand at the beginning of the verse in Hebrew, but they need to describe the consequences if I do not disclose ….

The Hebrew in the middle of this verse is difficult to make sense of. The original says “if I disclose it to you,” but the context seems to require a negative, “if I do not disclose it to you.” New Jewish Publication Society’s Tanakh, which faithfully follows the Masoretic Text in most cases, inserts the word “not” in the text within brackets. Many versions add the negation without any special punctuation, and others reword this part of the verse to convey the meaning “if my father intends to do you a mischief, I shall tell you so” (New Jerusalem Bible).

Disclose it to you: as in verse 12.

Trying to make sense out of difficult verses, Traduction œcuménique de la Bible translates verses 12b-13a as follows:
“If everything goes well for David and in that case I do not let you know, may the LORD do to Jonathan that and more. If it pleases my father to harm you, I will warn you, and send you away and you will go peacefully.”

Quoted with permission from Omanson, Roger L. and Ellington, John E. A Handbook on the First and Second Books of Samuel, Volume 1. (UBS Helps for Translators). New York: UBS, 2001. For this and other handbooks for translators see here .