Chasidut zu Tehillim 8:78

And these three correspond to the three [items] mentioned previously. For we can recognize the existence of God, by way of the heavens and the earth. This is like their statement, may their memory be blessed, “When Avraham died, [God] hung [Avraham’s healing stone] upon the sphere of the sun” (Bava Batra 16b); and like the Rambam, may his memory be blessed, wrote (Mishneh Torah, Foundations of the Torah 2:2), “and when [a person] will think of all these matters, and those like them, he will be taken aback and stricken with awe.” And it is like David said, “When I behold Your heavens, etc. (Psalms 8:4). And knowledge of the truth of the Torah is [attained] by way of circumcision. For the Jewish people are one of [God’s] acquisitions (Pesachim 87b), since we were acquired by him as His slaves – and it is customary that when one acquires a slave for life, a tag is placed upon [that slave]. And since we are his slaves, we are obligated to do [His will] – as it is written, “today upon your hearts,” such that they should be in your eyes like new items every day (Deuteronomy 6:6 with Rashi) – just like we run to find out a [new] decree of a king. And hence circumcision (brit) has a numerical equivalent (gematriya) of 612; and with [the addition of] this commandment, itself, it adds up to 613. Therefore, one who rejects idolatry is as if he assents to the entire Torah (Kiddushin 40a); as the main thing is that he takes on the yoke of the kingdom of Heaven upon himself – ‘and the rest is commentary.’ And the third is [knowledge of the existence of] reward and punishment; and it is felt by way of the Shabbat, which is ‘a taste of the world to come, the day of Shabbat rest.’ And therefore Scripture opened with, “In the beginning,” to hint about the three of them together, since they are the purpose of existence – the creation and the day came ‘together with circumcision.’