The most unambiguous reference comes in Antya Khanda of Chaitanya Bhagavata:
When Chaitanya Mahaprabhu arrived in Ramakeli news quickly spread everywhere, His loud roaring, kirtana, crying, and His appeal to everyone to chant the holy name of Hari
attracted the attention of even the infidels. When the local constable
related the topics of this wonderful ...
One such reference is found in the Chaitanya Bhagavata:
pṛthivīte āche yata nagarādi grāma
sarvatra pracāra haibe mora nāma
In every town and village throughout the world, the chanting of my name will be heard. (Chaitanya Bhagavata, Antya Khanda, 4.126)