At a minimum, the notion of humankind made in the image of God necessarily implies the inherent worth (sacredness) of each person.
The first Biblical source of that notion is found in Genesis:
Gen 1:26–27 (NIV)
26 Then God said, “Let us make mankind in our image, in our likeness, so that they may rule over the fish in the sea and the birds in the sky, over the livestock and all the wild animals, and over all the creatures that move along the ground.”
27 So God created mankind in his own image, in the image of God he created them; male and female he created them.
Gen 5:1, 2
This is the written account of Adam’s family line.
When God created mankind, he made them in the likeness of God. 2 He created them male and female and blessed them. And he named them “Mankind” when they were created.
6 “Whoever sheds human blood,
by humans shall their blood be shed;
for in the image of God
has God made mankind.
In Christianity, alone, there is a wide range of interpretations of “made in the image of God” ranging from humanity as a manifestation of God, more specifically, in Jesus, himself, to a notion of Trinity (either coequal or modes of manifestation of the Divine), to the notion that we are the “hands and feet of God” to “do God’s will.” One enlightened Christian interpretation of the meaning of “created in the image of god” is expressed in the Michelangelo masterpiece on the ceiling of the Sistine Chapel, Creation of Adam.
In that the Old Testament is recognized as sacred scripture of Judaism and Islam, as well as Christianity, those traditions each have their own perspective on what it means to be “created in the image of God,” not so dissimilar from the range of Christian views on various theological matters.
Hinduism recognizes the one supreme God, Brahma, to be manifest in all of nature as, creator, sustainer, and destroyer. Some might interpret these manifestations as a Hindu counterpart of the Christian notion of Trinity. Based upon the central belief that Brahma exists in all things, it would hold that all humanity is divine. The Indian custom of greeting another with a bow and hands together, as though in prayer, is a customary Hindu acknowledgement of the divinity in the other.
Buddhism is unique among the world religions in that it holds no concept of God. That view perhaps may best be described in the words of the second century CE Buddhist philosopher, Ngarjun:
We know the gods are false and have no concrete being;
Therefore the wise man believes them not
The fate of the world depends on causes and conditions
Therefore the wise man may not rely on gods.
In the secular world, some similar notions relating to the special nature of humankind are expressed in such phrases as “dignity of life” and “inalienable rights.” Although efforts have been made to obtain a world consensus on the meaning of these and similar phrases through the United Nations and other world bodies, their meaning remains elusive of common interpretation and implementation.