Akhfā
Most hidden — center of the chest
Akhfā, the 'most hidden' — at the centre of the breastbone. Its light is green, the colour of Khiḍr and of the Prophetic Reality (al-haqīqa al-Muḥammadiyya). It is the seat of the divine secret of unity (sirr al-tawḥīd) and, in Sirhindī's reading, the latifa where baqāʾ — subsisting after annihilation — becomes possible. This is the latifa associated with the Prophet Muhammad himself and is regarded as the most central, properly speaking, of the chest-lataif.
Point 5 of 6 in Lataif al-Sitta (Six Subtle Centers)
Cross-tradition overlaps
No overlapping points are registered for this point.
Sources
Sirhindī, Maktūbāt I.260 (primary_canonical)
Maktūbāt I.260 (First Daftar, Letter 260) describes akhfā as the most hidden of the chest latāif at the breastbone and associates it with the Muhammadan centre. The green light and baqā language belong to the later Mujaddidi interpretive vocabulary.
William Chittick, Sufism: A Beginner's Guide (secondary)