"Thou shalt not covet" (Exodus 20:17) is one of the Bible's famous Ten Commandments. It is also mentioned in the Yoga Sutras of Patanjali, referred to as Asteya or non-covetousness, one of the five Yama principles, and in the Tao Te Ching. In simple terms, the meaning of non-coveting is not to hoard things. Instead, one must be generous and giving. However, the deeper, more subtle meaning is much more important to understand.
Coveting creates a scarcity mindset. It sends out the signal to the universe that we don't have enough of this, be it love, money, or whatever, and thus we fail to allow any more into our lives. Saying, "I don't have enough of this, so I must hoard it." is a surefire way of not attracting any more of it. Whereas saying, "I am grateful for everything I have" (no matter how much that is) and openly giving to others creates a vibration that allows more to come in.
The ever-changing phenomenal world is one of flow. That is its nature. So coveting, be it physically or mentally, is to go against the natural flow of the universe, and if one does so, whatever we hoard will naturally and inevitably be taken away by one means or another.
Amass a store of gold and jade and no one can protect it
Lao Tsu (Tao Te Ching: v.9)
Trust this ancient wisdom because it teaches us the state of effortless being. Where one is not attached to one's possessions and life is seen to, and allowed to, happen within you.
It is the movement of life, and it is also the movement of love. The more your heart is open, the more love there is in the world, and the more your life will reflect that love in abundance.
With an open mind, you will be openhearted
Being openhearted, you will act royally
Being royal, you will attain the divine
Being divine, you will be at one with the Tao
Lao Tsu (Tao Te Ching: v.16)