The bhikṣā (accepting food etc. by going to houses for collecting them in conformity with the canonical instruction) received by a monk who goes to the house of a householder without any pre information and without disclosing his identity.
ajñātoñchaṃ paricayākaraṇenājñātaḥ san bhāvoñchaṃ gṛhasthodvaritādi.
(Da 9.3.4 HāVṛ Pa 253)