Therefore every Israelite is bound to observe only such of the 613 precepts as are possible to him; and such as he has not observed in consequence of hindrances arising from unpreventable causes will be reckoned to him as if actually performed.
The Yalkut Shimeoni, in true Rabbinical style, amplifies still farther the license conceded in the above quotations. Rabbi Eliezer says that the Israelites bewailed thus before God, exclaiming, "We would fain be occupied night and day in the law, but we have not the necessary leisure." Then the Holy One--blessed be He!--said, "Perform the commandment of the Phylacteries, and I will account it as if you were occupied night and day in the study of the law."
Anyhow, all the precepts are being observed by all Israel taken together, viz, the priests observe their part, the Levites theirs, and the Israelites theirs; thus the whole keep all. For the Holy One--blessed be He!--has written a law for His faithful servants, the nation of Israel, and as a nation they keep the whole law. It is as once when a king wrote to his subjects thus, "Behold, I command you to prepare for war against the enemy; raise the walls higher, collect arms, and store up victuals;" and those that were builders looked after the walls, the armorers after the weapons, the farmers after the stores of food, etc., etc. Each, according to his ability, did all that was required of him, and all unitedly fulfilled the king's command.
He who neglects to observe any of the 613 precepts, such as were possible for him to observe, is doomed to undergo transmigration (once or more than once) till he has actually observed all he had neglected to do in a former state of being.
The sages of truth (the Kabbalists) remark that Adam contains the initial letters of Adam, David, and Messiah; for after Adam sinned his soul passed into David, and the latter having also sinned, it passed into the Messiah. The full text is, "They shall serve the Lord their God, and David their king, whom I will raise up to them" (Jer. xxx. 9); and it is written, "My servant David shall be their king forever" (Ezek. xxxvii. 25); and thus "They shall seek the Lord their God, and David their king" (Hosea iii. 5).