金石之交

Explanation: Attn: friendship. Friendship as solid as stone 　　Usage: Partial official; as object; with compliment, referring to a deep friendship, 　　Source: Han Ban Gu "Han Han Xin Chuan": "Although a single step from that to pay with HW as the stone, then the final for the Kingship of the birds carry on." Thesaurus:  friends in days of simple living, Year-end parties companion in adversity, Bao Guan companion in adversity, sworn brothers and sisters companion in adversity, Absolute sincerity Centre at, Stone pay