Genesis 38:18
And he said, What pledge shall I give thee? And she said, Thy signet, and thy bracelets, and thy staff that is in thine hand. And he gave it her, and came in unto her, and she conceived by him. And he said, What pledge shall I give thee? And she said, Thy signet, and thy bracelets, and thy staff that is in thine hand. And he gave it her, and came in unto her, and she conceived by him.
The pledge of signet, bracelets, and staff was given in the course of Judah's illicit union with Tamar his daughter-in-law, who had put herself out of her usual path and appearance so that he did not recognize her, and by that meeting she conceived Pharez. That conception made Pharez a child born of harlotry. The episode belongs to the moral failures and family troubles that followed Jacob's having more than one wife, including jealousy, low moral standards, and crime.
The record of Judah's sin is given to expose sin so that it will be shunned, not to encourage lust or excuse wrongdoing, and to point to God's love, mercy, and power as the remedy. Pharez, born of this harlotry, stands in the human ancestry of Christ, with Tamar named among the women in Jesus' ancestry, showing that his earthly family line was marked by reproach, human sin, and weakness. That line concentrated in Christ all the weaknesses, passions, and sinful tendencies of fallen humanity.
Christ therefore took flesh not of sinless man but of sinful man, subject to infirmity because the race had deteriorated physically and morally. This was necessary so he could suffer death, be tempted and sympathize, and redeem man. This family history offers hope to the fallen, even to those with inherited tendencies and appetites.
Although time, place, speech, clothing, ignorance, and forgetfulness can hide people from one another and estrange human love and knowledge, as when Judah failed to know Tamar, the Lord is not subject to such limits. His eye as his essence is everywhere, always over his own, and he knows who are his.