Why did the Prophet, sallallaahu ‘alayhi wa sallam, combine the act of not purifying oneself after urination (or not taking cover from people's sight) with the act of tale-bearing in the Hadeeth of the torment of the grave? [Al-Bukhaari]

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

The reason behind combining the torment of the person who does not purify himself properly after urination and does not take cover from people’s sight while urinating  and the one who is a tale-bearer is that the Prophet, sallallaahu ‘alayhi wa sallam, passed by the two graves whose dwellers were being tortured. He, sallallaahu ‘alayhi wa sallam, told his Companions about their punishment and so he had to mention the reasons behind this, which were their not purifying themselves properly after urination and not taking cover from people while urinating  and bearing tales. 

And Allaah Knows best.