Here's why:
* "His embrace" is a noun phrase. "Embrace" is the noun, and "his" is a possessive pronoun modifying it.
* Adjectives describe nouns. There is no adjective present in this phrase.
You could use an adjective to describe the embrace, for example:
* His sweet embrace
* His warm embrace
* His gentle embrace
In these examples, "sweet," "warm," and "gentle" are adjectives modifying the noun "embrace."