Yoga Sutras 2.39
Patanjali, explained by Swami Vivekananda
अपरिग्रहस्थैर्ये जन्मकथन्तासंबोधः ॥
aparigrahasthairye janmakathantāsaṃbodhaḥ
When he is fixed in non-receiving, he gets the memory of past life.
In plain words: When a person completely stops accepting gifts and owning more than they need, they remember their past lives. The teacher says such a person stays free and independent, and this memory makes them determined to be free from rebirth.
Swami Vivekananda explains
When a man does not receive presents, he does not become beholden to others, but remains independent and free. His mind becomes pure. With every gift, he is likely to receive the evils of the giver. If he does not receive, the mind is purified, and the first power it gets is memory of past life. Then alone the Yogi becomes perfectly fixed in his ideal. He sees that he has been coming and going many times, so he becomes determined that this time he will be free, that he will no more come and go, and be the slave of Nature.