Rav Avigdor Miller on How to Console the Mourner
Q:
What is the best consolation to give someone who is sitting shiva, lo aleichim v’lo aleinu?

A:
To console people, the best thing is to come and show yourself. That’s the consolation. Just by honoring him by coming, that’s already a consolation.

Now, if it’s somebody who’s really broken up, then you have to use words that are suited to the occasion. But you cannot give one prescription that suits everybody. If a person is of a philosophical bent of mind, so you talk to him about Olam Habah and about this world being only a temporary place; you can talk about how a man who deserves reward was taken by Hakodosh Boruch Hu to Gan Eden, and he’s being now treated to all the great promises that Hakodosh Boruch Hu promised to those who serve Him. Whatever it is, there are ways and means of consoling each person according to his seichel.

Some people are obtuse; they’re not intelligent so you can’t tell them anything. So all you can say is, “Vusmachstu cousin Jake?” That’s all you can say. Now, vusmachstu you shouldn’t say because that’s sh’eilas shalom, it’s a greeting (see Yoreh Dei’ah 385:1), but you speak to him about mundane ordinary things, and that’s the only consolation you can give a man without any brains. So it all depends according to his seichel.