What Vedas say about DEATH and Rebirth of the human body?

Human body is mentioned in VEDAS as tri-ani pada (three bodies in one) - divine, spiritual and gross. Atma (soul) - the omniscient principle resides in divine body, spirit (JIVA) - the energy principle resides in spiritual body along with ten Pranas (vital breaths / Asu), Vivek (discernment), Buddhi (intellect).

According to Rig Veda 1-2-7 Pranas/Asu is the great devourer of diseases. Billions of cells along with senses/sense organs and etani -outward looking mind reside in our gross body. Atma (soul) is not affected by MAYA the cosmic delusion. Since Maya hides the Truth and Reality with its Golden Lid, and this dazzling golden disc (extreme Materialism in the vast sea of turbulent matter) affects senses and sense organs, so the existence of Soul as Reality remains hidden from the senses. 

Beneficent spirit is provided to us to perform our right deeds. Good thoughts relate to the soul. Thus, human mind (manas) is completely joined with soul and spirit but under the influence of senses, phenomenal world of matter it is de-linked from these divine inner instruments and is badly entangled with matter, lust, greed infatuation and attachment. One of the purposes of human birth is mentioned “realisation of one’s Real Self”. For Self Realisation Vedas prescribe “Follow RTA (cosmic laws) which having been created even God follows sternly.” By following RTA and Dharma, one can realise the Real Self in one birth.  

What happens at the time of Death of the gross body? Vedic Description

At the time of death of the gross body, cells merge with the earth, Spirit (Jeev) merges with the divine Nature (Prakrti), the human Soul being immortal remains alive, and hence consciousness remains. Based on degree of truth, quality of Karma (good or bad deeds), acquired in the present and previous births as individual's running ledger account, it gets manifested again on the birth of another gross body. This process of birth and rebirth continues until, the soul achieves perfection, is released from the three modes of Prakrti and moves beyond three gunas of transparency, activity and passivity. It is the stage of salvation, liberation i.e. Vedic Moksha.

Rig Veda 1-164-20, 10-9-20, 10-8-43 and 44 describe three divine substance, Parmatma, (Supreme Soul), Atma (human soul) and the divine Nature Prakrti. On the “Death” of human beings, Spirit goes back to Prakrti and merges with the Nature as part of the vast storehouse of energy. The Soul does not go back to Parmatma who is the Supreme Soul as it gets affected with subtle atoms and particles of human good and bad deeds, thoughts and desires.

Vedic metaphysics is emphatic that owing to the prevalence of the spirit of God in all human beings, any distinction of class superiority or inferiority is negation of religion and ethics.

Soul is dynamic but not moving when manifested, but moves faster than all material things when not manifested. It traverses billions of miles when it goes to devas (formless beings of light as forces of divine Nature) viz. Suriya (Sun), Chandrama (Moon), Indra, Mitra, Varun, Yama etc., during the 12 days journey after the death of gross body for purification, knowledge, luster, noble and divine traits, which it lost during the stage of manifestation in the body. (Yajur Veda 39-6). However, the effects of Karma remain intact. It becomes fierce, calm, terrible, fearless, ignorant, enlightened, passionate or ascetic dependent on the past deeds, desires and thoughts (Y.V.39-7). In the womb it becomes lovely through various virtuous deeds, chastise able through ignoble deeds, supreme through divine knowledge, noble through spiritual force and protector of all bodily organs and the pericardium enclosing the heart. It is for this reason that most of the scriptures mention the soul dwelling in the heart of all individuals. Apart from Vedas, Bhagavad-Gita, Adi Grantha Gaund M-5 and Katha Upanishad 1-2-20 to 22 also mention the soul residing in the heart.

After its 12 days journey, it is well equipped with Vedic knowledge, a-priori principles and cosmic laws of social and moral order (Rta). Thus on the birth of a child, the knowledge of four Vedas is made available through the manifested soul which is part of the inner world.

Thus consciousness is the real cause of transmigration of soul from one body to another. Brihadarnyaka Upanishad 4-3-34 and 4-4-4 explains the rebirth as a man passes from dream to wakefulness, so does from this life to next life. At old age or during the stage of degeneration even during young age, the self separates from the limbs like ripe mango, fig or banayan fruit separates itself from the trunk. The same way the self hastens to his new abode based on past karma and begins a new life in a new body. The "self" i.e. atma departs through eye, or gate of the skull or some other apertures of the body. The deeds of the entire life and the impressions those deeds created to the manifested soul before leaving the body follows the individual in the next birth.

Even those Souls which have achieved Moksha and have become one with God also take birth after centuries to guide the harassed humanity. Some time they take birth through divine potency like Lord Krishna or Lord Rama and most often as human beings with normal birth like Buddha, Mahavira, Socrates, Sankracharya and many others. 

From the above description, it is apparent that true followers of Vedic guidelines observe Prayer Meetings of the departed souls on the 13^th day of the death as the departed soul completes its journey for purification on the 12^th day.