The Ohr HaChaim reads Moshe's repeated request as spiritually profound and explores why the divine refusal came despite his fervent prayer. This is one of the strongest later commentators on the passage.
וָאֶתְחַנַּן אֶל ה׳ בָּעֵת הַהִוא לֵאמֹר. צָרִיךְ לָדַעַת אָמְרוֹ בָּעֵת הַהִוא. וְרַבּוֹתֵינוּ זִכְרוֹנָם לִבְרָכָה אָמְרוּ (ספרי דברים כו) כְּשֶׁרָאָה שֶׁנָּפַל סִיחוֹן וְעוֹג לְפָנָיו וְכוּ׳, לְדִבְרֵיהֶם חוֹזֵר לְמַה שֶׁלְּפָנָיו שֶׁהִיא מִלְחֶמֶת סִיחוֹן וְעוֹג, וּלְפִי זֶה טַעַם הַמַּאֲמָר לוֹמַר שֶׁזּוּלַת מַה שֶׁהָיָה בָּעֵת הַהִיא לֹא הָיִיתִי מִתְפַּלֵּל כִּי הַגְּזֵרָה כְּבָר נִגְזְרָה. עוֹד נִתְכַּוֵּן לְדַיֵּק אַרְבָּעָה תְּנָאִים הַצְּרִיכִין לְקַבָּלַת תְּפִלָּה: אֶחָד, שֶׁיִּתְפַּלֵּל כְּעָנִי הַדּוֹפֵק עַל הַפֶּתַח, כְּדֶרֶךְ אָמְרוֹ (משלי יח:כג) ״תַּחֲנוּנִים יְדַבֶּר רָשׁ״. ב׳, שֶׁיְּבַקֵּשׁ מִמְּקוֹר הָרַחֲמִים. ג׳, זְמַן הַתְּפִלָּה, כְּדֶרֶךְ אָמְרוֹ (תהלים סט:יד) ״וַאֲנִי תְפִלָּתִי לְךָ ה׳ עֵת רָצוֹן״. ד׳, שֶׁתִּהְיֶה תְּפִלָּתוֹ מְפֹרֶשֶׁת וְלֹא תִהְיֶה סוֹבֶלֶת פֵּרוּשׁ בִּלְתִּי הָגוּן, וּכְמַעֲשֶׂה שֶׁהוּבָא בַּמִּדְרָשׁ (אסתר רבה פ״ז:כד) בְּהַהוּא גּוֹי וְיִשְׂרָאֵל וְכוּ׳, וְיָלְדָה בְּהֶמְתּוֹ שֶׁל גּוֹי וְאָנַס יִשְׂרָאֵל לְהַרְכִּיבוֹ עַל כְּתֵפוֹ וְכוּ׳, עַד כָּאן. וְהוּא מַה שֶׁנִּתְכַּוֵּן מֹשֶׁה בְּמַאֲמָרוֹ כָּאן: וָאֶתְחַנַּן – לְשׁוֹן תַּחֲנוּנִים, זֶה כְּנֶגֶד תְּנַאי רִאשׁוֹן. אֶל ה׳ – שֶׁבִּקֵּשׁ מִמְּקוֹר הָרַחֲמִים, זֶה כְּנֶגֶד תְּנַאי שֵׁנִי. בָּעֵת הַהִיא – פֵּרוּשׁ בָּעֵת הַיְּדוּעָה לְקַבָּלַת תְּפִלָּה שֶׁהִיא עֵת רָצוֹן, כִּי מִי יוֹדֵעַ עֵת הָרָצוֹן כְּמֹשֶׁה. וְאֶפְשָׁר שֶׁזֶּה הָיָה בְּעֵת אֲשֶׁר אָמַר לוֹ ה׳ ״הָחֵל רָשׁ״ אֶרֶץ סִיחוֹן וְעוֹג, וְזֶה מְכֻוָּן לְדִבְרֵי רַבּוֹתֵינוּ זִכְרוֹנָם לִבְרָכָה שֶׁאָמְרוּ לְאַחַר שֶׁכָּבַשׁ אֶרֶץ סִיחוֹן וְעוֹג וְכוּ׳, זֶה כְּנֶגֶד תְּנַאי שְׁלִישִׁי. לֵאמֹר – פֵּרוּשׁ, פֵּרֵשׁ אֲמָרָיו כַּמִּצְטָרֵךְ שֶׁלֹּא יִסְבְּלוּ דְּבָרָיו דָּבָר בִּלְתִּי הָגוּן, זֶה כְּנֶגֶד תְּנַאי רְבִיעִי. וּלְדִבְרֵי רַבּוֹתֵינוּ זִכְרוֹנָם לִבְרָכָה שֶׁאָמְרוּ ״בָּעֵת הַהִיא״ כְּשֶׁרָאָה מִלְחֶמֶת סִיחוֹן וְעוֹג, טַעַם אָמְרוֹ לֵאמֹר נִמְשֶׁכֶת עִם ״אַתָּה הַחִלּוֹתָ״. וּכְבָר כָּתַבְתִּי בְּכַמָּה מְקוֹמוֹת כִּי כְּשֶׁאֵינוֹ אוֹמֵר הַדִּבּוּר בִּלְשׁוֹן עַצְמוֹ שֶׁאֲמָרוֹ אֶלָּא כּוֹלֵל הַמְּכֻוָּן בְּלָשׁוֹן אַחֵר, הוּא אוֹמֵר ״לֵאמֹר״ – פֵּרוּשׁ, כַּוָּנַת הַמַּאֲמָר הִיא זֹאת. כְּמוֹ כֵן בְּמַה שֶׁלְּפָנֵינוּ אָמַר ״לֵאמֹר״ לְהָעִירְךָ עַל זֶה. וְיֵשׁ מֵרַבּוֹתֵינוּ זִכְרוֹנָם לִבְרָכָה שֶׁאָמְרוּ (ילקוט שמעוני יט) ״בָּעֵת הַהִיא״ כְּשֶׁאָמַר לוֹ (במדבר כ:יב) ״לֹא תָבִיאוּ אֶת הַקָּהָל״ וְגוֹ׳, וְיֵשׁ שֶׁאָמְרוּ (מדרש רבה) כְּשֶׁאָמַר לוֹ (במדבר כז:יח) ״קַח אֶת יְהוֹשֻׁעַ״ וְגוֹ׳. וְאֶפְשָׁר שֶׁבְּכָל הָעִתִּים הִתְפַּלֵּל וְעַל כָּל עֵת מֵהֶם הוּא אוֹמֵר ״בָּעֵת הַהִיא״, וְאֵלּוּ וָאֵלּוּ דִּבְרֵי אֱלֹהִים חַיִּים.
ואתחנן אל ה׳ בעת ההיא לאמור, "I pleaded with G'd at that time, saying, etc." Why did Moses have to say "at that time?" Sifri writes that when Moses saw how Sichon and Og had fallen, he believed that the fact that he had lived to see this was proof that G'd had relented in His decree against him and that this was an opportune time to plead to be allowed to enter the West Bank. If we accept this interpretation the words בעת ההיא refer to the time of the wars with Sichon and Og. Moses excused himself saying that had it not been for what he had been allowed to witness at that time he would not have pleaded for G'd to rescind His decision seeing he was aware that the decree was final. Moses' entreaty also demonstrated four conditions which are necessary in order for one's prayer to be accepted. 1) One needs to pray in a manner similar to a poor man who knocks on a door in order to obtain some alms or some food as a hand-out, as we have been taught in Proverbs 18,23: "the poor man speaks beseechingly." 2) The prayer must be addressed to the source of Mercy, i.e. G'd Himself in His capacity as the attribute of Mercy. 3) It must be offered at a time when prayers are accepted, as we know from Psalms 69,14: "May my prayer to you come at a favourable moment, etc." 4) The prayer must be specific, incapable of being interpreted wrongly. This point is illustrated by Esther Rabbah at the beginning of chapter 7 item 24. [The Midrash discusses the meaning of the words in Esther 3,14: "that the people should be ready for this date," without specifying what precisely they should expect to happen on that day. The point is made that predictions made by Gentile prophets are obscure, liable to be misunderstood, whereas predictions made by Jewish prophets are clear and unambiguous. Ed.] The example quoted concerns a Jewish traveller who tired of the long trek he had to walk and whose ankle gave out. He said: "I wish I had a donkey." Shortly thereafter a Roman whose ass had just given birth to a young donkey passed him and told him to take it and to carry it. The traveller acknowledged that his prayer had been heard but that he had not expressed his prayer appropriately. He had failed to specify for what purpose he had requested the donkey. Thus far the Midrash. The word ואתחנן is the appropriate terminology when one beseeches G'd. By using this word Moses had complied with the first of the four conditions needed for a successful prayer. When he added אל השם, he complied with the second condition, i.e. he addressed his prayer to the attribute of Mercy. When he said בעת ההיא, he indicated that he had waited for the appropriate moment to offer up his prayer, i.e. a moment when G'd was known to be in a favourable frame of mind. Who would know better when such a time occurred than Moses? Perhaps this had been at the moment when G'd had said החל רש, "begin to possess and inherit his land" (Deut. 2,31). This would be in line with the view of our sages who said that Moses offered this prayer after the Israelites had defeated Sichon and Og and conquered their lands. By having waited for the appropriate time Moses had complied with the third of the four conditions for successful prayer we have listed earlier. Moses complied with the fourth condition for successful prayer when he said לאמור, i.e. he was precise in the formulation of his prayer, making it impossible to misunderstand. I have pointed out repeatedly that the word לאמור is often used to indicate that whatever immediately precedes it does not necessarily describe the exact words being used. Some of our commentators such as the author of the Yalkut Shimoni hold that the words בעת ההיא, "at that time," refer to Numbers 20,12 when G'd had told Moses and Aaron: "you (both) will not bring this community to the land I have given to them." On the other hand, Midrash Rabbah claims that the time Moses offered this prayer was on the occasion of Numbers 27,18 when G'd had told Moses to appoint Joshua as his successor. It is possible that Moses prayed a similar prayer on each of the occasions mentioned.