Verse 19: And Samuel (1 Sam. 2:21) grew, and (Gen. 39:2, 21, 23) the LORD was with him, (1 Sam. 9:6) and did let none of his words fall to the ground.
[Now, Samuel grew] That is, as he grew in stature, so also in God’s grace and favor (Vatablus). Likewise before men in the reputation of extraordinary holiness (Sanchez).
Samuel grew, as in stature, so in wisdom and piety, and God’s favour, and reputation with the people.
[And the Lord was with him] Supporting him, and increasing him with His gifts (Menochius).
[None of all his words fell to the ground, וְלֹֽא־הִפִּ֥יל מִכָּל־דְּבָרָ֖יו אָֽרְצָה׃] And He did not cause to fall (or, permit to fall [English, Dutch, similarly Junius and Tremellius], or cast aside, or cast down [Munster, Tigurinus]) of all his words to the ground (Montanus, Pagnine, Vatablus). [Indeed, they render the entire verse in this way: And so, Samuel, perceiving that the Lord was with him (Syriac, Arabic), cast down none of all His words to the ground (Syriac). He was not slothful, nor was he neglecting any matter of those things that the Lord was commanding him (Arabic).] Thus in Esther 6:10, let not any word fall to the earth; that is, omit nothing. Οὐ χαμαὶ πεσεῖται ὅτι ἄν εἴποις, what thou hast said shall not fall to the ground: Plato (Gataker). Thus Lively. The sense of the passage: Whatever he said, or predicted, happened; nothing failed (Drusius, similarly Sanchez, Lapide, Mendoza, Vatablus, Munster, Menochius). Of all the words of him, namely, Samuel; or, as others prefer, God; there was nothing that was not fulfilled in action (Mendoza). Samuel did not set forth a single word that was vain and empty. Others refer it to God, He did not allow any word of His to be made void (Vatablus). To cast to the ground is the same thing as to set forth an idle word, a word that brings forth no fruit; or to make a word void (Munster). It is a Hebraism, and is used elsewhere: in Joshua 21:45, not has fallen a word, etc.; in 1 Kings 8:56; 2 Kings 10:10; Luke 16:17 (Mendoza). Thus, Cicero, perhaps unto this purpose, said, Letters 9, He speaks what falls to the ground (Sanchez). Now, it is a Metaphor, taken, either, 1. From seed, which, having been sown, God blessed (Junius). But then he would have said, it did not fall to the earth in vain; for seeds fall to the earth: But none of these words fell to the earth (Drusius). Or, 2. From gladiators, or soldiers; who in their martial, or training, encounters work at this, that their thrusts should not prove ineffective, or poorly aimed; that is, that the spear, which was bound to pierce the body of the enemy, missing that, should not be fixed in the earth (Sanchez): Or, 3. From liquids; which, if they be poured out upon the earth, are lost; or from collapsed buildings (Vatablus, Lapide, similarly Piscator); in which many things waste away, are scattered, are broken (Lapide). Moreover, what perishes and is destroyed is said to fall to the earth; as in Matthew 10:29, a sparrow does not fall to the earth (Drusius).
Fall to the ground, that is, want its effect or success; God made good all his predictions. A metaphor from precious liquors, which when they are spilt upon the ground, are altogether useless and ineffectual. This phrase is oft used, as Joshua 21:45; Esther 6:10, etc.
 Hebrew: וַיִּגְדַּ֖ל שְׁמוּאֵ֑ל וַֽיהוָה֙ הָיָ֣ה עִמּ֔וֹ וְלֹֽא־הִפִּ֥יל מִכָּל־דְּבָרָ֖יו אָֽרְצָה׃  Esther 6:10: “Then the king said to Haman, Make haste, and take the apparel and the horse, as thou hast said, and do even so to Mordecai the Jew, that sitteth at the king's gate: let nothing fail of all that thou hast spoken (אַל־תַּפֵּ֣ל דָּבָ֔ר מִכֹּ֖ל אֲשֶׁ֥ר דִּבַּֽרְתָּ׃).”  Edward Lively (1545-1605) was an English linguist and Biblical scholar, serving as Professor of Hebrew at Cambridge (1575-1605). He wrote a commentary on the Minor Prophets and a chronology of the Persian monarchs; and he was heavily involved in the planning of the Authorized Version.  Joshua 21:45: “There failed not ought of any good thing (לֹֽא־נָפַ֣ל דָּבָ֔ר מִכֹּל֙ הַדָּבָ֣ר הַטּ֔וֹב) which the Lord had spoken unto the house of Israel; all came to pass.”  1 Kings 8:56: “Blessed be the Lord, that hath given rest unto his people Israel, according to all that he promised: there hath not failed one word of all his good promise (לֹֽא־נָפַ֞ל דָּבָ֣ר אֶחָ֗ד מִכֹּל֙ דְּבָר֣וֹ הַטּ֔וֹב), which he promised by the hand of Moses his servant.”  2 Kings 10:10: “Know now that there shall fall unto the earth nothing of the word of the Lord (לֹ֙א יִפֹּ֜ל מִדְּבַ֤ר יְהוָה֙ אַ֔רְצָה), which the Lord spake concerning the house of Ahab: for the Lord hath done that which he spake by his servant Elijah.”  Luke 16:17: “And it is easier for heaven and earth to pass, than one tittle of the law to fail (πεσεῖν, to fall).”