the 'characteristic qualities of a Stream-winner' are 4:

• unshakable faith towards the Enlightened One,

• unshakable faith towards the Doctrine,

• unshakable faith towards the Order, and

• perfect morality.

Explained in S.LV.1, D.33, in S.XLVII.8 and in Netti-ppakarana these 4 qualities are called sotāpattiyanga (q.v.).