Halakha Yeremia 22:10: Kitzur Shulchan Arukh & Shulchan Arukh, Yoreh De'ah

It is forbidden to grieve excessively over the dead, as it is said, "Do not weep for the dead, and do not bemoan him."¹Jeremiah 22:10. Our Sages of blessed memory, said,²Masechess Moed Kattan 27b. "Is it possible to say so? But it means, "Do not weep for the dead excessively, and do not bemoan him inordinately." How should one mourn? Three days are appropriate for weeping, seven days for mourning, and thirty days for abstaining from wearing ironed clothes, and from having the hair cut. Thereafter the Holy One, blessed is He, says, "You are not permitted to show him more compassion than I do." Our Sages, of blessed memory, said,³Ibid. "One who grieves excessively over the dead, will have cause to weep over another death." This applies only when the deceased was an ordinary person, but if he was a Torah scholar, he is mourned in proportion to his wisdom. Nevertheless, you should not weep over him more than thirty days, for he is not greater than Moshe Rabbeinu, peace unto him, of whom it is written, "And the Children of Yisrael wept for Moshe thirty days."⁴Deuteronomy 34:8.

One should not grieve excessively for the dead, and whosoever grieves excessively for him, will weep for another [dead]¹M.K. 27b in accord with Rab Judah on the authority of Rab. save that three days [are designated] for weeping, seven for lamenting, thirty [to abstain from] cutting the hair and wearing laundried garments.²M.K. ibid., for it is written, “‘Weep ye not for the dead, neither bemoan him” (Jer. XXII, 10), which is explained as follows: ‘“Weep ye not for the dead” — excessively; “neither bemoan him” — beyond measure. In what matter? — Three days for weeping and seven for lamentation etc.’ (ibid.).