Those who mourn, as if they did not; those who are happy, as if they were not; those who buy something, as if it were not theirs to keep (NIV)
And those who weep and mourn as though they were not weeping and mourning, and those who rejoice as though they were not rejoicing, and those who buy as though they did not possess anything, (AMP)
And they that weep, as though they wept not; and they that rejoice, as though they rejoiced not; and they that buy, as though they possessed not; (KJV)