[One of the young men told] This servant acted prudently and faithfully; perhaps he was also moved by his own danger (Martyr).
One of the young men told Abigail; wisely considering the mischievous effects likely to follow so churlish a message.
[So that they might bless, etc., לְבָרֵ֥ךְ אֶת־אֲדֹנֵ֖ינוּ] To bless (that is, salute) our masters. Thus he speaks in the plural concerning one, Nabal, for honor’s sake; or he also included Abigail herself (Malvenda).
[He shunned them, וַיָּ֥עַט בָּהֶֽם׃]] And (I would prefer, but [Piscator]) flew upon them (Montanus, Pagnine, Tigurinus, Mariana, Kimchi in Munster), that is, with harsh words (Piscator, similarly Mariana). A Metaphor from an עַיִט, bird of prey, which flies upon its food (Piscator). He scorned them (Munster, similarly Jonathan, Syriac); he derided them (Arabic); he rebuffed them (Junius and Tremellius). He sent them away immediately, as if he forced them to fly from his harsh and uncivil response (Vatablus). He declined from them (Septuagint).
[Good] Benignant (Vatablus), helpful (Piscator).
[Nothing was lost, וְלֹא־פָקַדְנוּ]] We did not miss, or desire: that is, we did not miss anything lost, since nothing was ever lost (Vatablus).
Verse 16: They were (Ex. 14:22; Job 1:10) a wall unto us both by night and day, all the while we were with them keeping the sheep.
[For a wall were they] Against the Philistines (Grotius), or wild beasts and robbers (Piscator).
A wall, that is, a defence against wild beasts, and robbers, and enemies.
Verse 17: Now therefore know and consider what thou wilt do; for (1 Sam. 20:7) evil is determined against our master, and against all his household: for he is such a son of (Deut. 13:13; Judg. 19:22) Belial, that a man cannot speak to him.
[Malice is completed, כָלְתָ֧ה הָרָעָ֛ה] Determined (completed [Pagnine], perfected, as in 1 Samuel 20:7 [Piscator], decreed [Vatablus]) is evil (Junius and Tremellius, Vatablus, Piscator), namely, destruction. A Synecdoche of genus, which the article indicates (Piscator). Decreed is misfortune, understanding, that it comes; that is, it is most certainly going to come: that is to say, otherwise was it done concerning our master and his family (Vatablus). He was gathering this from the words and indications of the messengers (Menochius); from the spirit and character of David, which his servants knew from long experience (Sanchez).
Evil is determined against our master; which it was easy to guess; either from some threatening expressions which David’s men used; or from the consideration of David’s great power, and that rage which so high a provocation was likely to produce in military persons.
[And he is a son of Belial, such that no one is able to speak to him,וְהוּא֙ בֶּן־בְּלִיַּ֔עַל מִדַּבֵּ֖ר אֵלָֽיו׃] Verbatim: And he is a son of Belial (without worth [Montanus]) from speaking (to address [Montanus]) with him (Vatablus) (to him [Malvenda]); he is too wicked, or worthless, than that one might be able to address him (Pagnine, similarly the Septuagint), than (more than [Piscator]) that I might address him (Junius and Tremellius). And that man is wicked to speak with him (Jonathan). Others otherwise: since he, as a son of Belial, spoke against him (Munster). He appears to have taken מִדַּבֵּר, either as the participle מְדַבֵּר/ speaking, or as מִתְדַבֵּר, but it conjoins the want of the characteristic ת. [The Hithpael readily supplies the Dagesh (ּ) in the ד/Daleth.] Concerning the term Belial, see Deuteronomy 13:13. The sense: He is too wicked than that one might be permitted to speak to him concerning this matter (Vatablus). No one could speak, etc. Such that he would not receive some rude response (Menochius).
A man cannot speak to him, to wit, without hazard to himself, and therefore I acquaint thee rather than him with this matter.
 Hebrew: וְלַאֲבִיגַ֙יִל֙ אֵ֣שֶׁת נָבָ֔ל הִגִּ֧יד נַֽעַר־אֶחָ֛ד מֵהַנְּעָרִ֖ים לֵאמֹ֑ר הִנֵּ֣ה שָׁלַח֩ דָּוִ֙ד מַלְאָכִ֧ים׀ מֵֽהַמִּדְבָּ֛ר לְבָרֵ֥ךְ אֶת־אֲדֹנֵ֖ינוּ וַיָּ֥עַט בָּהֶֽם׃  Hebrew: וַיָּ֥עַט בָּהֶֽם׃. עִיט can signify to scream/screech, or to dart upon.  Hebrew: וְהָ֣אֲנָשִׁ֔ים טֹבִ֥ים לָ֖נוּ מְאֹ֑ד וְלֹ֤א הָכְלַ֙מְנוּ֙ וְלֹֽא־פָקַ֣דְנוּ מְא֔וּמָה כָּל־יְמֵי֙ הִתְהַלַּ֣כְנוּ אִתָּ֔ם בִּֽהְיוֹתֵ֖נוּ בַּשָּׂדֶֽה׃  Hebrew: הָכְלַמְנוּ. פָּקַד signifies to muster, to visit, to seek, to seek in vain or to miss.  Hebrew: חוֹמָה֙ הָי֣וּ עָלֵ֔ינוּ גַּם־לַ֖יְלָה גַּם־יוֹמָ֑ם כָּל־יְמֵ֛י הֱיוֹתֵ֥נוּ עִמָּ֖ם רֹעִ֥ים הַצֹּֽאן׃  Hebrew: וְעַתָּ֗ה דְּעִ֤י וּרְאִי֙ מַֽה־תַּעֲשִׂ֔י כִּֽי־כָלְתָ֧ה הָרָעָ֛ה אֶל־אֲדֹנֵ֖ינוּ וְעַ֣ל כָּל־בֵּית֑וֹ וְהוּא֙ בֶּן־בְּלִיַּ֔עַל מִדַּבֵּ֖ר אֵלָֽיו׃  1 Samuel 20:7: “If he say thus, It is well; thy servant shall have peace: but if he be very wroth, then be sure that evil is determined by him (כִּֽי־כָלְתָ֥ה הָרָעָ֖ה מֵעִמּֽוֹ׃).” בְּלִי signifies without; יַעַל, worth, use, profit(  The Hithpael participle, without significant change of meaning.