Genesis 38:1

“And it came to pass at that time, etc.] This some refer to the time of Jacob’s coming from Padanaram into Canaan, soon after he came to Shechem, and before the affair of Dinah; but to this may be objected the marriage of Judah at an age that may seem too early for him, his separation from his brethren, and having a flock of his own to keep, which seems not consistent with the above history: wherefore it is better to connect this with the history of Joseph’s being sold into Egypt; for though there were but twenty three years from hence to Jacob’s going down into Egypt, Joseph being now seventeen, and was thirty years when he stood before Pharaoh, after which were seven years of plenty, and…”

“JUDAH AND FAMILY. (Gen. 38:1-30) at that time--a formula frequently used by the sacred writers, not to describe any precise period, but an interval near about it.”

“- The Family of Judah 1. עדלם ‛ǎdûllâm, ‘Adullam, “righteousness.” חירה chı̂yrâh Chirah, “nobility?” 2. שׁוּע shûa‛, Shua‘, “luck, riches, cry.” 3. ער ‛êr, ‘Er, “watching.” 4. אונן 'ônân, Onan, “strong.” 5. שׁלה shēlâh, Shelah, “request? rest.” כזיב kezı̂yb Kezib, “falsehood.” 6. תמר tāmār, Tamar, “palm.” 12. תמנה tı̂mnâh, Timnah, “counted or assigned.” 14. עינים 'êynayı̂m, ‘Enaim, “two fountains.” 29. פרץ perets, Perets, “breach.” This strange narrative is an episode in the history of Joseph; but an integral part of the “generations” of Jacob. It is loosely dated with the phrase “at that time.” This does not indicate a sequel to the preceding record, the proper phrase for…”

“38:1-30 The story of Judah and Tamar is a carefully placed interlude; it reports what was happening in the family of Judah, who would later rise to prominence, and it shows the beginnings of assimilation with the people of the land to help explain why God sent the family to Egypt (chs 39–47). The Egyptians were strict separatists (43:32); the Israelites would retain their unique identity better in Egypt than in Canaan.”