This is also an extremely important and very subtle one. Again it is a very specific sentiment with a lot of personal feeling. Consider these are desert people, so tears are scarce. And yet, he sobbed until his beard was soaking in tears.
The grave is the first stage of the afterlife, a precursor of things to come.
128- ‘Abdullah al-Madini narrated that ‘Uthman’s servant Hani said: “Whenever ‘Uthman visited a grave, he sobbed until his beard was soaking in tears.”