It is better to go to the house of mourning - Birthdays were generally kept with great festivity, and to these the wise man most probably refers; but according to his maxim, the miseries of life were so many and so oppressive that the day of a man's death was to be preferred to the day of his birth. But, in dependently of the allusion, it is much more profitable to visit the house of mourning for the dead than the house of festivity. In the former we find occasion for serious and deeply edifying thoughts and reflections; from the latter we seldom return with one profitable thought or one solid impression.
That - Namely, what is seen in the house of mourning.
Lay it to his heart - Consider it attentively.