The concept of speaking as a unique and defining feature of humanity is indeed reflected in the Quran. Speech, as a means of communication and expression, is seen as a divine gift that distinguishes humans from other creatures. Here are a few references from the Quran that highlight this idea:

1. **The Gift of Speech**:
- "The Most Merciful, taught the Quran, created man, [and] taught him eloquence." (Surah Ar-Rahman, 55:1-4)

This verse highlights that the ability to articulate and communicate effectively (eloquence) is a direct gift from Allah, emphasizing its importance and uniqueness in humans.

2. **Honoring Humanity**:
- "And We have certainly honored the children of Adam and carried them on the land and sea and provided for them of the good things and preferred them over much of what We have created, with [definite] preference." (Surah Al-Isra, 17:70)

This verse underscores the honor and special status given to humans, which includes the gift of speech and communication.

3. **Responsibility of Speech**:
- "Not a word does he (or she) utter but there is a watcher by him ready to record it." (Surah Qaf, 50:18)

This highlights the significance and responsibility that comes with the ability to speak, as every word is recorded and holds weight.

Speech is not just a mode of communication but a reflection of our thoughts, intentions, and moral values. The Quran recognizes this power and guides believers to use it wisely and justly, thus reinforcing the notion that speech is a fundamental aspect of our humanity and our relationship with the divine.