Silsilah as-Sahihah 2617 — General greeting of Salam

It is narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "When one of you meets his brother, he should greet him with salam. If a tree, wall, or stone comes between them and then they meet again, he should greet him with salam once more."