مَرَرْتُ عَلَى مُوسَى لَيْلَةَ أُسْرِيَ بِي عِنْدَ الْكَثِيبِ الْأَحْمَرِ وَهُوَ قَائِمٌ يُصَلِّي فِي قَبْرِهِ
On the night I was taken on the Journey, I passed Moses near the red sand-hill, standing and praying in his grave. (Narrated by Anas; Sahih Muslim)
The report of Moses praying in his grave is particularly significant in support of barzakh life. This prayer is a distinctive worship of that intermediate realm.