Be'er Mayim Chaim, Genesis 37:35/באר מים חיים·בראשית ל״ז:ל״ה

2And its saying, all of his sons and all of his daughters, hints to it being in the way of that which [the sages], may their memory be blessed, said (Moed Katan 27b), "Anyone who cries too much for his deceased, will, God forbid, cry for another death." And that is why until the end of three days, his sons and his daughters did not arise to comfort him. Just the opposite, they cried with him. But after three days of mourning passed, then all of his sons and all of his daughters arose, etc. That is to say that it is appropriate for him to be concerned about his children and to be consoled by their words of comfort and to stop crying. Yet he refused to be consoled and said, "I will rather go down to the grave as a mourner". Meaning, I am not like others who cry for their dead, who will, as a result of this, be visited by something not good, God forbid. Rather, I am crying about myself, since the Holy One, blessed be He, told me, "This is a sign given over to you, that if none of your sons dies in your lifetime, you can be certain never to see Geihinnom," like the sages' statement, may their memory be blessed. (Rashi on this verse, and see Midrash Tanchuma, Vayigash 9.) And that is [the meaning of why] I am crying: Since, I will, God forbid, go down, etc. And that is why his father cried over him, and did not stop crying even after the three days.