Śatapatha Brāhmaṇa ("of a hundred paths") 6.6.2.16

6.6.2.16

bāhyokhā bhavati | antare muñjā bāhyo hyātmāntarā yonirvāhye muñjā bhavantyantare śaṇā bāhyā hi yonirantaraṃ jarāyu bāhye śaṇā bhavantyantaraṃ ghṛtam bāhyaṃ hi jarāyvantaramulbam bāhyaṃ ghṛtam bhavatyantarā samidvāhyaṃ hyulvamantaro garbha etebhyo vai jāyamāno jāyate tebhya evainametajjanayati

The pan is outside, and the reed-grass (fuel) is inside; for the body is outside, and the womb inside. The reed-grass is outside, and the hemp inside; for the womb is outside, and the outer membrane is inside. The hemp is outside, and the ghee is inside; for the outer membrane is outside, and the inner membrane is inside. The ghee is outside, and the kindling-stick is inside; for the inner membrane is outside, and the embryo is inside. It is from these that he who is born is born, and from them he thus causes him (Agni) to be born.