Jeremiah 32:14

Thus saith the Lord of hosts, the God of Israel; Take these evidences, this evidence of the purchase, both which is sealed, and this evidence which is open; and put them in an earthen vessel, that they may continue many days.

Cross-reference

Jeremiah 32:10-12 details the signing, sealing, and witnessing that the command to store the deeds in an earthenware vessel references.

Jeremiah 19:1 also uses an earthenware flask as a prophetic symbol—there for judgment, here for preservation.