Question: I recently paid a condolence visit to the mourners of an old friend and was somewhat taken aback by the nature of the conversation which was being conducted between the consolers and the mourners. What is the right thing to do and to say when making such a visit?
Answer: Since the principal objective of nichum aveilim, as we call the mitzvah of comforting mourners, is to relieve the grief suffered by those who lost a close relative, the very act of coming to their home during their shiva mourning period, regardless of what you say, expresses your empathy with their sorrow and relieves some of the agony of feeling alone in a time of tragedy.
Ideally, however, such a visit should provide both consoler and mourner with an opportunity to recall the virtues of the deceased in the same manner as the funeral provides the ones delivering the eulogies that opportunity. The concept behind this is that the judgment being conducted in Heaven for the soul of the deceased takes into account what the survivors on earth have to say about him.
Even more praiseworthy is conversation about the theological aspects of life and death with a stress on the mercy of Heaven expressed even in what appears to be a tragedy, on afterlife and resurrection. Such talk reinforces the mourner’s sense that death is not an end but rather a beginning. Once should be careful, however, to avoid saying "What can we do?" which our Talmudic sages viewed as a blasphemous suggestion that if it were in our power we would act against the Divine decision.
When you comfort the mourner, writes Rambam, you are also comforting the soul of the deceased. This may be the reason why the traditional blessing made by the comforter in the Ashkenazic community is said in the plural form "May the Omnipresent comfort you (you is in the plural in Hebrew) together with all the other mourners of Zion and Jerusalem and may you (plural) be spared further grief" even when there is a single mourner.