The Bible states that the unborn infant at any stage of development has a human soul and is the object of Christ’s salvation. We read:
The Lord called me before my birth; from within the womb He called me by name." Isaiah 49:1 (Living Bible)
Jer 1:5 "Before I formed you in the womb I knew a you…”
You were there when I was being formed in utter seclusion. You saw me before I was born, before I began to breathe! Psalm 139:15 (Living Bible)
Oh that I had been an untimely birth, as an infant which never saw the light. Then had I been at rest with kings and counselors of the earth, with princes that had gold. The small and the great are there. Job 3:16 (KJV)
If a man beget a hundred children, and live many years so that the days of his life be many, and his soul be not filled with good...I say that an untimely birth is better than he. He (the untimely or miscarried child) hath not seen the sun, nor known anything; yet this one hath more rest than the other. Ecc. 6:3-5 (KJV)
A child is human from the moment of conception. The Scriptures above describe the unborn as a complete individual with the pronouns "I," "my," or "me." It would not be possible for us to have identity or be human without body and soul.
To ask "at what point does a human fetus receive a spirit?" is to ask the wrong question. The Bible tells us that human beings are two elements: body and soul woven into one, Is. 10:18 , 51:23, Micah 6:7, Matt. 10:28, 1 Th. 5:23, Dan. 7:15, 1 Cor. 6:20, 1 Cor. 7:34, and James 2:26. Therefore we are body and soul at conception.
In view of the above passages we can conclude that when an embryo, of even a few days, is miscarried and lost to earthly existence, God completes the "substance" of the life He began into a heavenly, glorified body.
King David lost an infant shortly after birth. In 2 Sam. 12:18, this man of faith said, "He cannot come again to me, but I will go to him." What he meant was that the child was already in heaven.
The Bible speaks about the faith of John the Baptist in the womb. In Luke 1:44,
In Mark 10:14-16, Christ tells the parents to bring their children to Him, regardless of the child’s age and ability to reason. In Matt. 18:6, He says it would be better if a person were drowned with a millstone around his neck rather than interfere with the faith "of these little ones who believe in Me." The Greek word for "little ones" can mean as young as a fetus. What is implied here is that ‘little ones’ believe in their Maker.
Babies do not need the ability to reason in order to have faith in Christ. The power of salvation is in the Gospel. If the ability to reason was necessary for faith, then there would be a question about the salvation of the severely retarded, those who die in their sleep, or those who die while unconscious.
We would be judging God if we assumed that the untimely death of an infant meant God did not plan to save the unborn child. Christ came to save what He became. He first became a fetus in Mary’s womb. Therefore, He came to save the product of every conception in the womb. It says in the Bible, "He died for all." This means God also desires to save those who die in the womb.