Hizb 39 opens Juz 20, closing An-Naml before crossing into Al-Qasas, and by this point in the thirty-juz sequence a reciter has already encountered Moses's story in Al-Baqara, Al-Araf, Ta-Ha and Ash-Shuara; this hizb carries the version scholars typically point to as the most detailed account of his infancy and upbringing specifically, filling in material the earlier, more compressed retellings had assumed rather than narrated.
In tarawih recitation this hizb typically opens the twentieth night, marking the two thirds point of the whole Ramadan cycle, and congregations following the Moses material across several earlier hizb divisions often experience this hizb as filling in a gap rather than repeating what they had already heard, since the infancy material here has no real parallel elsewhere in the Quran.
Huffaz reviewing this hizb by quarter typically find the transition into new, previously unheard detail easier to retain than a further repetition of already familiar episodes would be, since fresh narrative content tends to anchor in memory more readily than a sixth telling of the same well known scenes.
Teachers introducing this hizb to students already familiar with the shorter Moses retellings elsewhere in the Quran often use it specifically to demonstrate how the thirty-juz scheme can hold both a summary and its own fuller expansion of the same events at very different points in the recitation cycle.