A true friend never walks away

क्षीरेणात्मगतोदकाय हि गुणाः दत्ताः पुरा तेऽखिलाः
क्षीरे तापमवेक्ष्य तेन पयसा ह्यात्मा कृशानौ हुतः ।
गन्तुं पावकमुन्मनस्तदभवद्दृष्ट्वा तु मित्रापदम्
युक्तं तेन जलेन शाम्यति सतां मैत्री पुनस्त्वीदृशी ॥

- नीतिशतकम्

Milk imparts its inherent qualities like sweetness to its constituent water. When it is boiled, the water on having seen the milk in distress immediately sacrifices itself to the fire (and evaporates). The milk in turn becomes eager to throw itself into the fire (by boiling over) on seeing the plight of its friend water. However, it settles down when some water is poured. Such is the nature of friendship of the virtuous.

A friend in need is a friend indeed.
It is prosperity that gives us friends, adversity that proves them.
A true friend sticks with you through thick and thin no matter what.