Etadaggaṁ, bhikkhave, samānattatānaṁ yadidaṁ sotāpanno sotāpannassa samānatto, sakadāgāmī sakadāgāmissa samānatto, anāgāmī anāgāmissa samānatto, arahā arahato samānatto.   The best kind of equality is the equality of a stream-enterer with another stream-enterer, a once-returner with another once-returner, a non-returner with another non-returner, and a perfected one with another perfected one.  

Cattāri sotāpannassa aṅgāni.   Four factors of a stream-enterer: