The Torah says:
וְשָׁמְר֥וּ בְנֵֽי־יִשְׂרָאֵ֖ל אֶת־הַשַּׁבָּ֑ת לַעֲשׂ֧וֹת אֶת־הַשַּׁבָּ֛ת לְדֹרֹתָ֖ם בְּרִ֥ית עוֹלָֽם׃ בֵּינִ֗י וּבֵין֙ בְּנֵ֣י יִשְׂרָאֵ֔ל א֥וֹת הִ֖וא לְעֹלָ֑ם כִּי־שֵׁ֣שֶׁת יָמִ֗ים עָשָׂ֤ה יְהוָה֙ אֶת־הַשָּׁמַ֣יִם וְאֶת־הָאָ֔רֶץ וּבַיּוֹם֙ הַשְּׁבִיעִ֔י שָׁבַ֖ת וַיִּנָּפַֽשׁ – Therefore the children of Israel shall keep the sabbath, to observe the sabbath throughout their generations, for a perpetual covenant. It is a sign between Me and the children of Israel for ever; for in six days the Lord made heaven and earth, and on the seventh day He ceased from work and rested.’ [Ex. 31:17]
I remember hearing long ago that the phrase "beni uven bnei Israel – between Me and the children of Israel" must be recited or sung very fast, to reflect the fact that there is no daylight between us Jews and God. (This is certainly done in the melodies I know.) If such a teaching really does exist, does anybody have a source for it?
Here is the version we sang in Egypt, by yours truly (1988).