Padīpopamasutta

sn54.8:15.1 Now, a mendicant might wish:

sn54.8:15.2 ‘Going totally beyond perceptions of form, with the disappearance of perceptions of impingement, not focusing on perceptions of diversity, aware that “space is infinite”, may I enter and remain in the dimension of infinite space.’

sn54.8:15.3 So let them closely focus on this immersion due to mindfulness of breathing.