Authentic Supplication Number 224.

It is reported about Abi Hurayrata  that he said: If one of you meets his brother then let him petition peace upon him, then, if a tree, a wall, or a stone should come between them let him petition peace upon him again upon meeting him.

Reporters.
'Al-`Adawee said this was reported by `Abu-Dawood on page 381 of volume 5. He said it was sound, due to a very similar hadeeth which was reported by Ibn As-Sunni in 'Al-Yawm was-Laylah as #245. These two are of completely different chains and each serves as a testimonial for the other making it sound. Further testimonial is found for this hadeeth in #1011 in 'Al-'Adab 'Al-Mufrad.