The Venerable Sāriputta describes his experience of the first jhāna.

Vivekaja sutta - Born From Seclusion

At one time, the Venerable Sāriputta was dwelling in Sāvatthi, in Jeta's Grove, Anāthapiṇḍika's park. Then, in the morning, having dressed and taken his bowl and robe, he entered Sāvatthi for alms. Having wandered for alms in Sāvatthi and after the meal, having returned from his alms gathering, he approached the Dark Forest for the day's abiding. Having entered the Dark Forest, he sat down at the root of a certain tree for the day's abiding.

Then, in the evening, having emerged from seclusion, he approached Jeta's Grove, Anāthapiṇḍika's park. The Venerable Ānanda saw Venerable Sāriputta coming from afar. Seeing him, Venerable Ānanda said:

"Your faculties are clear, friend Sāriputta; your facial complexion is pure and bright. In what dwelling have you dwelled today, Venerable Sāriputta?"

"Here, friend, secluded from sensual pleasures, secluded from unwholesome mental qualities, I entered and dwelled in the first jhāna, which is accompanied by reflection and examination, born from seclusion, and is filled with joyful pleasure. For me, friend, the experience was not characterized by thoughts such as 'I am entering the first jhāna,' 'I have entered the first jhāna,' or 'I have emerged from the first jhāna.'"

"Indeed, Venerable Sāriputta has long ago eradicated the underlying tendencies towards I-making, mine-making, and conceit. Therefore, for him, there is no such thought process as 'I am entering the first jhāna,' 'I have entered the first jhāna,' or 'I have emerged from the first jhāna.'"