(Pending — forward of Ch. 547: the full Impel Down self-sacrifice that lives up to this vow is forward-canon. See Bon Clay Friendship Doctrine Speech for the doctrine this escalates.)
Why this matters
Oda’s doctrine-restated-with-the-stakes-raised move: a character who already paid a price for a friendship (Alabasta) re-swears the same oath at a higher cost, in a setting engineered to demand it. The restatement of the Ch. 0156 / Ch. 0215 friendship doctrine — now aimed at one specific friend, with his life explicitly on the table — is the install for Bon Clay’s Impel Down sacrifice.