בֵּינִ֗י וּבֵין֙ בְּנֵ֣י יִשְׂרָאֵ֔ל א֥וֹת הִ֖וא לְעֹלָ֑ם כִּי־שֵׁ֣שֶׁת יָמִ֗ים עָשָׂ֤ה יְהוָה֙ אֶת־הַשָּׁמַ֣יִם וְאֶת־הָאָ֔רֶץ וּבַיּוֹם֙ הַשְּׁבִיעִ֔י שָׁבַ֖ת וַיִּנָּפַֽשׁ׃ (ס)
צװישן מיר און צװישן די קינדער פֿון ישׂראל איז דאָס אַ צײכן אױף אײביק, אַז זעקס טעג האָט גאָט געמאַכט דעם הימל און די ערד, און אױפֿן זיבעטן טאָג האָט ער אױפֿגעהערט און גערוט.
Rashi
וינפש AND WAS REFRESHED — Take it as the Targum renders it: ונח “and He rested”. Every form of נפש is derived from the noun נֶפֶש, soul; the idea is, that one calms his soul and takes breath when one reposes after the toil of labour. — And He of Whom it is written, (Isaiah 40:28) “[… the Lord, the Creator of the ends of the earth] fainteth not nor is He weary”, and Whose every action is accomplished by His mere command had the term “repose” written of (ascribed to) Himself in order to make comprehensible to the human ear what it can understand.
Da'at Zekenim
וביום השביעי שבת וינפש, “but on the seventh day He rested and withdrew into His essence.” Rabbi Yehudah Hachassid said that from this verse we can deduce that the Jew receives an additional soul on the Sabbath. When you read the respective last letters in the last four words of the verse backwards, you get the word שתים, “two.” The Talmud relates an interesting conversation between Rabbi Akiva and Turnusrufus, the wicked Roman governor during part of his life when the latter met him once on the Sabbath. Upon seeing him, the governor asked Rabbi Akiva what was so special on that particular day, to which Rabbi Akiva replied: “how are you different from anyone else?” Turnusrufus wanted to know what kind of an answer this was to his question. The Lord had singled him out to be more honoured than other human beings. Rabbi Akiva told him that the same Lord had singled out the Sabbath to be more honoured than any other day He had created. Turnusrufus then wanted to know why that same G–d performs all manner of work on the Sabbath, such as letting the wind blow, the rain fall, etc., whereas He denied the Jews to work on the Sabbath and to travel on the Sabbath? Rabbi Akiva replied that he was aware that the governor was familiar with the Torah G–d had given the Jews, so that he could ask him, why if two Jews share the same courtyard in front of their houses, what is the reason for the law whereby if each of the homeowners does not enter into an arrangement whereby he foregoes his legal claim to the courtyard, neither of them can move his chattels in that courtyard on the Sabbath, whereas when they each waive their claim, they can both use that courtyard freely? How come, he continued, that if a Jew has a palace owned exclusively by himself, and surrounded by a courtyard as large as the city of Damascus, he is free to move all his chattels all over that courtyard on the Sabbath? Similarly, the Lord Who owns both heaven and earth exclusively, is free to let the wind blow and to let the rain fall without thereby violating the laws of His Sabbath. He added, that if proof were needed for what he had told the Roman governor, let him reflect on the fact that that same Creator observed the Sabbath by not having given the Jews in the desert their heavenly bread, manna on that day, but giving them a double portion on the Sabbath eve, so that they would not go hungry on that day. (Tanchuma, section 33 on this portion)
Sforno
וביום השביעי שבת, seeing that on that day the creative activity of G’d had been completed, completion spells rest,