BG Chap 9 - Kṛṣṇa's promise
Kṛṣṇa tells Arjuna to declare to all that His devotee never perishes. Even if the devotee is sinful right till his death, he is not destroyed and at the time of death, he does not fall. If the smārtas do not consider such a person proper if he has not performed atonement rites, Kṛṣṇa with slight anger says that one should declare in the assembly of smārtas that His devotee, if he commits sinful acts out of negligence, will not be destroyed. Such a devotee will not become separated from Kṛṣṇa or attain misfortune. Remembrance of Kṛṣṇa is the most powerful atonement.
Why does Kṛṣṇa ask Arjuna to declare this instead of doing it Himself? Being affectionate to His devotee and not tolerating even a slight degradation of His devotee, Kṛṣṇa would under all circumstances uphold the declaration made by His devotee, whereas He could break His own promise and accept criticism. Just as, in breaking His own promise in fighting with Bhīṣma, He fulfilled Bhīṣma’s promise. Thus, hearing a declaration from His mouth, the materialistic disputers would laugh, but they would accept Arjuna’s declaration as written on stone. Therefore, Kṛṣṇa asks Arjuna to make the declaration.