New Defender's Study Bible Notes
38:18 What pledge. The Hebrew word for “pledge” is essentially the same as that for “surety” in Genesis 44:32, where Judah was offering himself to Joseph as a substitute to receive Benjamin’s punishment, instead of Benjamin. Similarly, Judah’s pledge was given to Tamar in substitution for the payment due to Tamar. Both, in effect, can be considered as types of Christ offering His own shed blood in substitution for the death our sins have deserved.
38:18 signet. A signet is a seal used as a signature to confirm a contract.