References – SN 35.69: Upasena 
Readings by Ajahn Pasanno:
Sutta: SN 35.60, Saḷāyatanasaṁyutta, “The Full Understanding of all Clinging.”
Sutta: SN 35.63, Saḷāyatanasaṁyutta, “Migajāla” (1).”
Sutta: SN 35.64, Saḷāyatanasaṁyutta, “Migajāla” (2).”
Sutta: SN 35.69, Saḷāyatanasaṁyutta, “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