References – SN 35.69: Upasena 
[Session] Readings by Ajahn Pasanno:
Sutta: SN 35.60, Saḷāyatanasaṃyutta, “The Full Understanding of all Clinging.”
Sutta: SN 35.63, Saḷāyatanasaṃyutta, “Migajāla” (1).
Sutta: SN 35.64, Saḷāyatanasaṃyutta, “Migajāla” (2).
Sutta: SN 35.69, Saḷāyatanasaṃyutta, “Upasena.”
The Fourth Foundation of Mindfulness [2013], Session 39
Discussion regarding Upasena being bitten by a snake in SN 35.69. [Great disciples] // [Family]
The Fourth Foundation of Mindfulness [2013], Session 39, Excerpt 6