Abba and Imma divide up into the First and Second Israel Sabba and Tevunah.
Abba and Imma divide into First and Second ISOT — producing the regular oscillation between First Maturity and Second Maturity (weekday and Shabbat).
Op. 128 specifies the structural mechanism of the regular oscillation. Abba and Imma have two operational modes — First ISOT and Second ISOT — that produce two operational intensities for Zeir Anpin (Z"A)'s governance.
First ISOT: the operational mode that produces First Maturity — the cosmic government's standard intensity, operating during the cycle's weekday-mode.
Second ISOT: the operational mode that produces Second Maturity — the cosmic government's higher intensity, operating during the cycle's Shabbat-mode and similar moments of special grace.
The oscillation is regular. It is not random or contingent on external factors; it is built into the cosmic government's structural-temporal architecture. Weekday and Shabbat alternate; the cosmic government oscillates with them. The cycle's micro-rhythm Op. 131 will name (weekday/Shabbat/holiday/night/day cycles) is the operational form of this oscillation.
The doctrinal-philosophical claim: the cycle of creation includes a regular oscillation between First and Second Maturity. The oscillation is not added to the cycle; it is part of the cycle's operational architecture. The cosmic government has two regular intensities — and Shabbat's higher intensity is built into the operational structure of Z"A, not added as a one-time feature.
Op. 129 (Z"A's First and Second Maturity in detail). Op. 131 (different times of ascent and descent — the macro-temporal architecture in which the regular oscillation sits).