Word

Tat ekam

Sanskrit

तत् एकम्

IAST

tat ekam

In General

By Tat ekam Samhita meant the Timeless unnamable truth behind all things. A mistake the modern speakers of Hinduism usually make is that only Upanishad represents the philosophy which says the ultimate unity of all things. But the word such as Tat ekam is said in all the four Veda Samhitas and the famous U. quotes such as tat tvam asi are only derivative of the Samhita quote.

Veda

ekam sat(R.V. 1.164.46) truth behind all things

Tat ekam R.V. 10.129.2

U. elaborated the idea of unity of all things to further height and had such famous quotes as Aham Brahmanasmi