This verse is from the Bhagavad Gita, Chapter 6, Verse 21. It is written in Sanskrit and translates to English as follows:
sukham ātyantikaṁ yat tad buddhi-grāhyam atīndriyam
vetti yatra na chaivāyaṁ sthitaśh chalati tattvataḥ || 21 ||
“That which is supreme bliss, which can be experienced only by the intellect and which is beyond the senses, having attained this state, the person never deviates and remains steady in the truth.”
In this verse, Lord Krishna tells Arjuna that by practicing yoga, a sadhak attains the supreme bliss (ultimate happiness) which is beyond the senses and can be understood only by the intellect. When a person attains this state, he becomes stable in this bliss and never again deviates from this state. This is the description of the highest state of yoga, where permanent peace and contentment is attained along with self-knowledge.
Sukham - bliss, happiness
Atyantikam - ultimate, final
Yat - that which
Tat - that
Buddhi-graahyam - that which can be grasped by the intellect
Atindriyam - beyond the senses
Vetti - knows, experiences
Yatra - where
Na - not
Cha - and
Eva - certainly
Ayam - this (yogi)
Sthita - stable
Chalati - moving, unmoved
Tattvatah - from the point of view of truth or reality