金兰之交

Explanation: Friendship as solid as stone 　　Source: "Han Han Xin Chuan": "Although a single step from the stone cross that with the HW, HW Suoqin But always carry on." Thesaurus:  friends in days of simple living, Year-end parties companion in adversity, Bao Guan companion in adversity, Absolute sincerity Centre at, close and intimate friend-ship, Stone pay