Simhasanadvatrimshika 19.2

19.2

dadāti pratigṛhṇāti guhyam ākhyāti pṛcchati,
bhuṅkte bhojayate cai 'va ṣaḍvidham prītilakṣaṇam. || 2 ||

2. Giving and receiving, telling secrets and asking about them, entertaining and being entertained, are the six marks of friendship.
3. Without a service rendered friendship can in no wise be conceived for any one. For even the gods grant the wishes of men in return for the gift of prayer.