Or at least, a thing you shouldn't say.
At a funeral/viewing/wake.
Do not go up to a random grieving person and announce that they should be envious of the deceased.
Really for any reason.
But supposing further within your statement that said deceased person is "in heaven" is a really bad reason. Such announcements should be met with handcuffs or fisticuffs. This is a statement not calculated to make the other person feel better. It is calculated to make YOU, the person stating such things, feel better, by referring to whatever comforting metaphysical beliefs about the afterlife and its relative importance vis a vis our physical existence you have and which may or may not be shared by others. It is therefore an inherently selfish act.
Showing up, saying you will be available if anything is needed in their time of grief, and so on, these are non-selfish pronouncements that should be socially accepted by anyone receiving them. Expressing relief that a deceased person is no longer suffering from some long-standing physical (or perhaps even psychological) malady also seems eminently sensible, though is neither comforting to the recipient nor a reason to be envious.
Further, examining such a statement for its underlying belief, it is precisely the sort of belief that is strongly associated to religious extremism and thus religious terrorism. When the current, known, physical existence is believed to be at a severe discount rate in moral terms, then virtually any action that is believed to be of higher relevance to some supposed (ie invented) eternal post-physical existence is taken to be acceptable. Hence, suicide squads attack.
If you value so little "life" in its mortal terms that we should be envious of the dead, then I'm not entirely sure what possible reason you would have for living (this is the inversion of the supposed argument that without such beliefs, including beliefs in afterlives, being imparted through religious orders, actual physical life is rendered meaningless and thus someone like me has no reason to live... which I find absurd. Presumably a religious zealot will attempt to tell me soon enough why I am being absurd here. Except there are obvious examples of zealotry run amok to point to as examples of what I am referring to here that give me some firmness, and the obvious example that I, and most other atheists, find meaning perfectly viable enough without having it imparted and without need for a baseless association with a post-materialistic existence).
So it doesn't surprise me when zealots take other people with them when they shuffle off the mortal coil and become late persons. And it should be reason enough to see people who would state such things as this to be watched carefully for the likelihood is greater that bombs and bullets may follow such words than for various other assaults on the conscience.
Score One for United Airlines
53 minutes ago