Avatarvad- incarnation of vishnu

ajaymano bahudha vijayate ...19/31 ch yajurveda

let me make it clear that the brahman supreme incarnates in lower form and that is vijayate .
this lower form as described in vedas is VISHNU and therefore the incarnation means the vishnu-avtars .

vishnu avtar mndlm 7 sukta 100

 Over this earth with mighty step strode Visnu, ready to give it for a home to Manu.
In him the humble people trust for safety: he, nobly born, hath made them spacious dwellings.
 To-day I laud this name, O gipivista, I, skilled in rules, the name of thee the Noble.
Yea, I the poor and weak praise thee the Mighty who dwellest in the realm beyond this region.
 What was there to be blamed in thee, O Visnu, when thou declaredst, I am Sipivista
Hide not this form from us, nor keep it secret, since thou didst wear another shape in battle....translation by sir ralph griffith
vi cakrame pthivim ea eta ketraya viur manue dasasyan | 
dhruvaso asya kirayo janasa urukiti sujanima cakara || 
pra tat te adya sipivia namarya sasami vayunani vidvan | 
ta tva ghami tavasam atavyan kayantam asya rajasa parake || 
kim it te vio paricakyam bhut pra yad vavake sipivio asmi | 

ma varpo asmad apa ghuha etad yad anyarupa samithe babhutha ||  4, 5 , 6 

वि चक्रमे पर्थिवीम एष एतां कषेत्राय विष्णुर मनुषे दशस्यन |
धरुवासो अस्य कीरयो जनास उरुक्षितिं सुजनिमा चकार ||
पर तत ते अद्य शिपिविष्ट नामार्यः शंसामि वयुनानि विद्वान |
तं तवा गर्णामि तवसम अतव्यान कषयन्तम अस्य रजसः पराके ||
किम इत ते विष्णो परिचक्ष्यम भूत पर यद ववक्षे शिपिविष्टो अस्मि |
मा वर्पो अस्मद अप गूह एतद यद अन्यरूपः समिथे बभूथ ||