Imperturbable and Serene is Samatha Calm..

The Blessed Buddha once said:
Knowing that the
other person is angry, the one who remains just calmly
aware acts for his own best interest, and for the others' interest, too!
Samyutta Nikāya I, 162
Exalted in mind while acutely alert is the sage trained
in sagacity's ways..
Such calmed and ever aware One has neither any sorrows,
nor any regrets...
Udana IV, 7
Calmed is his mind. Calmed is his speech. Calmed is his
behaviour.
So is the
tranquillity of one freed by the insight of right
understanding...
Dhammapada
96

More on this sweetly silenced Tranquillity
(Passaddhi):
https://What-Buddha-Said.net/drops/Forest_Bliss.htm
https://What-Buddha-Said.net/drops/IV/Silenced.htm
https://What-Buddha-Said.net/drops/III/Feeding_Tranquillity.htm
https://What-Buddha-Said.net/drops/III/Tranquillity_Passaddhi.htm