"When the LORD your God enlarges your border" (Deuteronomy 12:20). This is what Scripture says: "A man's gift makes room for him" (Proverbs 18:16). Because a person gives a gift from what is his, the Holy One, blessed be He, makes room for him. There was an incident with Avun the swindler, who lived in Bozrah. His teachers went there seeking sustenance. He would sit and not pledge first, until all the people of the city had pledged, for he wanted to know how much they were pledging, in order to pledge against all of them. Therefore he was called Avun the swindler, for he would deceive concerning all the commandments. Once he knew how much all the people of the city had pledged, he pledged against all of them. What did our Rabbis do? They took him and seated him at its edge beside them, to fulfill what is said, "A man's gift makes room for him." Another interpretation: "A man's gift makes room for him" -- this is Abraham. When he pursued the five kings, the king of Sodom came out to meet him and said to him, "Give me the persons and take the goods for yourself" (Genesis 14:21). Abraham said, "I have lifted my hand to the LORD, God Most High, that I will not take a thread or a sandal strap..." (Genesis 14:22-23). The Holy One, blessed be He, said to him: You said "a thread"; by your life, I will fulfill for your children with this very word, "How beautiful are your steps in sandals" (Song of Songs 7:2). Hence, "A man's gift makes room for him." Another interpretation: "A man's gift makes room for him" -- these are Israel. When the Holy One, blessed be He, told them to bring a freewill offering, what is written there? "And they brought to him still more freewill offerings morning by morning" (Exodus 36:3) -- two mornings. What did they merit? He enlarged their border, as it is said, "When the LORD your God enlarges your border." By what merit does He enlarge it? "As He has spoken to you" -- by the merit of the Ten Commandments that you received. Another interpretation: "As He has spoken" -- by the merit of your fathers.
When the Lord Enlarges Your Territory This Is What Is Stated
Midrash Tanchuma, Re'eh 5
כִּי יַרְחִיב ה' אֱלֹהֶיךָ אֶת גְּבֻלְךָ. זֶה שֶׁאָמַר הַכָּתוּב: מַתָּן אָדָם יַרְחִיב לוֹ (משלי יח, טז). מַתָּנָה בִּשְׁבִיל שֶׁאָדָם נוֹתֵן מִשֶּׁלּוֹ, מַרְחִיב לוֹ הַקָּדוֹשׁ בָּרוּךְ הוּא. מַעֲשֶׂה בַּאֲבוּן רַמָּאָה שֶׁהָיָה דָּר בְּבָצְרָה. הָלְכוּ רַבּוֹתָיו לְשָׁם וּמְבַקְּשִׁים פַּרְנָסָה. הָיָה יוֹשֵׁב וְלֹא פָּסַק תְּחִלָּה עַד שֶׁפָּסְקוּ כָּל בְּנֵי הָעִיר, שֶׁהָיָה רוֹצֶה לֵידַע כַּמָּה הֵם פּוֹסְקִין, כְּדֵי לִפְסֹק כְּנֶגֶד כֻּלָּן. לְכָךְ נִקְרָא אֲבוּן רַמָּאָה, שֶׁהָיָה מְרַמֶּה עַל כָּל הַמִּצְוֹת. מִשֶּׁיָּדַע כַּמָּה פָּסְקוּ כָּל בְּנֵי הָעִיר, פָּסַק כְּנֶגֶד כֻּלָּן. מֶה עָשׂוּ רַבּוֹתֵינוּ. נְטָלוּהוּ וְהוֹשִׁיבוּהוּ עַל שְׂפָתָהּ אֶצְלָם, לְקַיֵּם מַה שֶּׁנֶּאֱמַר: מַתָּן אָדָם יַרְחִיב לוֹ. דָּבָר אַחֵר, מַתָּן אָדָם יַרְחִיב לוֹ, זֶה אַבְרָהָם, כְּשֶׁרָדַף אַחַר חֲמִשָּׁה הַמְּלָכִים, יָצָא מֶלֶךְ סְדוֹם לִקְרָאתוֹ, אָמַר לוֹ: תֵּן לִי הַנֶּפֶשׁ וְהָרְכוּשׁ קַח לָךְ (בראשית יד, כא). אָמַר אַבְרָהָם, הֲרִימוֹתִי יָדִי אֶל ה' אֵל עֶלְיוֹן, אִם מִחוּט וְעַד שְׂרוֹךְ נַעַל וְגוֹ' (שם פסוק כב כג). אָמַר לוֹ הַקָּדוֹשׁ בָּרוּךְ הוּא, אַתָּה אָמַרְתָּ מִחוּט, חַיֶּיךָ, אֲנִי מְקַיֵּם בּוֹ בַּלָּשׁוֹן אֶת בָּנֶיךָ, מַה יָּפוּ פְּעָמַיִךְ בַּנְּעָלִים (שה״ש ז, ב). הֱוֵי, מַתָּן אָדָם יַרְחִיב לוֹ. דָּבָר אַחֵר, מַתָּן אָדָם יַרְחִיב לוֹ, אֵלּוּ יִשְׂרָאֵל, כְּשֶׁאָמַר לָהֶם הַקָּדוֹשׁ בָּרוּךְ הוּא לְהָבִיא נְדָבָה, מַה כָּתוּב שָׁם, וְהֵם הֵבִיאוּ אֵלָיו עוֹד נְדָבָה בַּבֹּקֶר בַּבֹּקֶר (שמות לו, ג), שְׁנֵי בְּקָרִים. מַה זָּכוּ. הִרְחִיב אֶת גְּבוּלָם, שֶׁנֶּאֱמַר: כִּי יַרְחִיב ה' אֱלֹהֶיךָ אֶת גְּבֻלְךָ. בִּזְכוּת מַה הוּא מַרְחִיבוֹ. כַּאֲשֶׁר דִּבֶּר לָךְ, בִּזְכוּת עֲשֶׂרֶת הַדִּבְּרוֹת שֶׁקִּבַּלְתֶּם. דָּבָר אַחֵר, כַּאֲשֶׁר דִּבֶּר בִּזְכוּת אֲבוֹתֶיךָ.