Yoga Sutras 2.30
Patanjali, explained by Swami Vivekananda
अहिंसा-सत्यास्तेय-ब्रह्मचर्यापरिग्रहा यमाः ॥
ahiṃsā-satyāsteya-brahmacaryāparigrahā yamāḥ
Non-killing, truthfulness, non-stealing, continence, and non-receiving are called Yamas.
In plain words: The first part of yoga is the Yamas, five rules for how we treat others. They are: do not harm or kill, tell the truth, do not steal, control sexual desire, and do not take gifts. The teacher explains that taking gifts can make you feel you owe the giver, so you lose your freedom.
Swami Vivekananda explains
A man who wants to be a perfect Yogi must give up the sex idea. The soul has no sex; why should it degrade itself with sex ideas? Later on we shall understand better why these ideas must be given up. The mind of the man who receives gifts is acted on by the mind of the giver, so the receiver is likely to become degenerated. Receiving gifts is prone to destroy the independence of the mind, and make us slavish. Therefore, receive no gifts.