As your enquiry is , I am herewith enlisting some of the verses mainly from Taittiriya Samhita of Krishna yajurveda and Shatapatha Brahmana Of Shukla Yajurveda. In Taittiriya Samhita we find many direct references about lifespan of human being i.e. of 100 years. We can also notice that a single mantra is repeated lots of places to denote this 100 years of lifespan , instead of separate mantra for this topic , a single sentence is repeated. The mantra in most of the references about 100 years of lifespan of humans is - शतायुः पुरुषः शतेन्द्रियः - Shatayu Purusha Shatendriya
Lets see some of them :-
from Taittiriya Samhita
KANDA 1- PRAPATHAKA 5
Here an example of Pankti Meter is used for 100 years lifespan of a man. The Pankti meter are 100 syllables and man lives a hundred years.
हिरण्यम् अभवत् तस्माद् रजतम् | हिरण्यम् अदक्षिण्यम् अश्रुजम् |
हि यो बर्हिषि ददाति पुरास्य संवत्सराद् गृहे रुदन्ति तस्माद्
बर्हिषि न देयम् । ।T.S 18.104.22.168 । ।
Brahmans desirous of holiness did not aforetime eat his food; the
Yajyas and Anuvakyas are in the Pankti metre; the sacrifice is
fivefold, man is fivefold; verily making recompense to the gods for
the hero he re-establishes the fire 1. They are of a hundred
syllables; man lives a hundred years and has a hundred powers;
verily he rests on life and power.
KANDA 1- PRAPATHAKA 7
This is a prayer to Agni so that a man could kindle the Agni for 100 years. That means a person could live for 100 years praying and worshiping Agni.
हिमा इत्य् आह शतं त्वा हेमन्तान् इन्धिषीयेति वावैतद्
नाम गृह्णात्य् अन्नादम् एवैनं करोति ताम् आशिषम् । ।T.S 22.214.171.124 । ।
O Agni, may I shine', he says; that is according to the text. 'Be
rich the sacrifice; may I be rich', he says; verily he invokes this
blessing. Within the Garhapatya much variegated work is performed;
with two verses to Agni, the purifier, he pays reverence to the
Garhapatya; verily he purifies the fire, he purifies himself; (he
uses) two for support. 'O Agni, lord of the house', he says 4;
that is according to the text. 'For a hundred winters', he says; 'for a hundred winters may I kindle thee', he says in effect. He
utters the name of his son;
KANDA 2 - PRAPATHAKA 3
शतकृष्णलां निर् वपेत् प्रजापतिम् एव स्वेन भागधेयेनोप धावति |
एवास्मिन्न् आयुर् दधाति सर्वम् आयुर् एति शतकृष्णला भवति |
शतायुः पुरुषः शतेन्द्रियः । आयुष्य् एवेन्द्रिये । ।T.S 2.3.2 । ।
The gods were afraid of death; they had recourse to Prajapati for them
he offered this (offering) to Prajapati of a hundred Krsnalas in
weight verily by it he bestowed upon them immortality; for him who
fears death he should offer to Prajapati this (offering) of a hundred
Krsnalas: verily he has recourse to Prajapati with his own share;
verily he bestows life upon him; he lives all his days. It is of a
hundred Krsnalas in weight; man has a hundred (years of) life, and a
Similarly we find the description in T.S. 126.96.36.199 , 7.5.9 etc.
From Shatapatha Brahmana
We also find references about 100 year life span of Human beings in Shatapatha Brahmana .
Kanda 2, adhyaya 3, brahmana 3 ,Mantra 6
- Hence it has been said by the Ṛṣis (Rig-veda I, 89, 9), 'A hundred autumns (may there he) before us, O gods, during which ye
complete the life-time of our bodies, during which sons become
fathers! do not cut us off, midway, from reaching the full term of
life!' for he (Agni) who is the son, now in his turn becomes the
father: this, then, is why one must establish the fires.
Here we can clearly see that the full term of life of human beings is said to be 100 years.
Kanda 4 , adhyaya 3, brahmana 4 , Mantra 3
- Now at the Haviryajña, indeed, they give as little as six or twelve (cows1), but no Soma-sacrifice should have dakṣiṇās of less than a
hundred. For he, Prajāpati2, forsooth, is the visible sacrifice; and
man is nearest to Prajāpati, and he has a life of a hundred years, a hundred powers, a hundred energies.
From Isha Upanishad
And this well known verse from Ishavasya Upanishad which is indicating that a good lifespan of human being is about 100 years. and he should desire to live that long , because it is declared by the vedas a such . This is also confirmed from Commentary of Adi Shankaracharya on this mantra.
कुर्वन्नेवेह कर्माणि जिजीविषेत् सतं समाः |
एवं त्वयि नान्यथेतोऽस्ति न
कर्म लिप्यते नरे… || 2 ||
kurvanneveha karmāṇi jijīviṣet sataṃ samāḥ
nānyatheto'sti na karma lipyate nare…
‘In the world, one should desire to live a hundred years, but only by
performing actions. Thus, and in no other way, can man be free from
the taint of actions.’
we must try to live our lives to the full span, and the full span of life, according to the Vedas, is one hundred years: Shatāyur vai purushah. Says Shankaracharya in his commentary:
This Atharva Veda Mantra is chanted at the time of ceremony of wearing first garments to new born baby by parents. Here the Mantra pray to various powers of gods so that child could live long life (upto 100 years) . This mantra is indirect reference towards ideal lifespan of Human Beings.
Kanda 2 - Sukta 13 - Mantra 4
एह्यश्मानमा तिष्ठाश्मा भवतु ते तनु : |
कृण्वन्तु विश्वे देवा
आयुष्टे शरद : शतम ||AV. 2.13.4||
Thou for our w eal hast clothed thee in the mantle: thou hast become
our heifers' guard from witchcraft. Live thou a hundred full and
plenteous autumns, and wrap thee in prosperity of riches.
O child come sit firmly on this rock ,so that your skin will become
firm as rock. May the godly powers make your age of 100 years.
Alternate translation of above mantra - :