Three sources using the terminology (in Hebrew) from the "River to the Sea" to describe this specific piece of land as the land that God has promised to the descendants of Abraham, Isaac and Jacob.
בַּיּ֣וֹם הַה֗וּא כָּרַ֧ת יהוה אֶת־אַבְרָ֖ם בְּרִ֣ית לֵאמֹ֑ר לְזַרְעֲךָ֗ נָתַ֙תִּי֙ אֶת־הָאָ֣רֶץ הַזֹּ֔את מִנְּהַ֣ר מִצְרַ֔יִם עַד־הַנָּהָ֥ר הַגָּדֹ֖ל נְהַר־פְּרָֽת׃
כׇּל־הַמָּק֗וֹם אֲשֶׁ֨ר תִּדְרֹ֧ךְ כַּֽף־רַגְלְכֶ֛ם בּ֖וֹ לָכֶ֣ם יִהְיֶ֑ה מִן־הַמִּדְבָּ֨ר וְהַלְּבָנ֜וֹן מִן־הַנָּהָ֣ר נְהַר־פְּרָ֗ת וְעַד֙ הַיָּ֣ם הָאַֽחֲר֔וֹן יִהְיֶ֖ה גְּבֻלְכֶֽם׃
מֵהַמִּדְבָּר֩ וְהַלְּבָנ֨וֹן הַזֶּ֜ה וְֽעַד־הַנָּהָ֧ר הַגָּד֣וֹל נְהַר־פְּרָ֗ת כֹּ֚ל אֶ֣רֶץ הַֽחִתִּ֔ים וְעַד־הַיָּ֥ם הַגָּד֖וֹל מְב֣וֹא הַשָּׁ֑מֶשׁ יִֽהְיֶ֖ה גְּבוּלְכֶֽם׃
God repeating the instructions and boundary of the Land to Joshua, son of Nun
The book of Joshua, the first book of Prophets, deals primarily with the process of Israel’s inheritance of the land of Canaan, from the crossing of the Jordan until the completion of Israel’s conquest of the land and its division among the tribes. Despite the myriad details enumerated, some relating to the actions of the people and some listing names and locations, there is a single theme running through the book. The book of Joshua completes the narrative that began in Deuteronomy, thus connecting it to the five books of the Torah. Indeed, these books are connected in several regards: The Torah concludes with the death of Moses, but the story of the people’s return to the land of the patriarchs is not yet complete. Moses was not granted permission to cross the Jordan, and it is therefore Joshua, who was ordained by Moses and who received some of Moses’ “grandeur,” who will act in place of Moses. Now Joshua will assume the role that was supposed to belong to Moses as he leads the people into the land and divides it among them. The Sages teach: Had Israel not sinned, they would have been given only the five books of the Torah and the book of Joshua. Indeed, the book of Joshua differs from the other books of Prophets in that it deals with the fulfillment of Israel’s mission, while the others are mostly reactions to Israel’s sins and issues.
Every spot on which your foot treads I give to you, as I promised Moses.
מֵהַמִּדְבָּר֩ וְהַלְּבָנ֨וֹן הַזֶּ֜ה וְֽעַד־הַנָּהָ֧ר הַגָּד֣וֹל נְהַר־פְּרָ֗ת כֹּ֚ל אֶ֣רֶץ הַֽחִתִּ֔ים וְעַד־הַיָּ֥ם הַגָּד֖וֹל מְב֣וֹא הַשָּׁ֑מֶשׁ יִֽהְיֶ֖ה גְּבוּלְכֶֽם׃
Your territory shall extend from the wilderness and the Lebanon to the Great River, the River Euphrates [on the east]—the whole Hittite country—and up to the Mediterranean Sea on the west.
Additional sources
David defeated Hadadezer, king of Zobah-hamath, who was on his way to set up his monument at the Euphrates River.
Moses giving over God's instructions to the Israelites before they cross into the Land of Israel over 3400 years ago (1100 BCE)
Deuteronomy Chapter 11
(הירש.)