Jesus was mentioned in the Vedic literatures
more than 3000 years before He appeared.

In the book called Bhavishya Purana there's a very nice and concise overview of the mission and mood of Jesus the Son of God.

We have clear written evidence from the ancient scriptures of India, written down more than five thousand years ago by the great sage Srila Krishna Dvaipayana Veda Vyasa that the coming of Christ (The Son of God) was a genuine incident where the Lord sent His pure devotee to perform a particular function among a particular group of people in a particular tract of land. In Bhavishya Purana He is referred to specifically as Isha Putra - "the Son of God".

In the following excerpt from a lecture of our Founder Acarya Srila A.C. Bhaktivedanta Swami Prabhupada he clearly points out how the Lord sends His partial expansion in the form of empowered being for functionary aspects of fulfilling His works. These empowered beings in the Sanskrit language of India are termed saktyavesha avataras.

"Lord Buddha, Jesus Christ, they are counted as saktyavesha avataras. They are also incarnations of saktyavesha, powerful, in this way the Supreme Lord manifest all over the universes." (A.C. Bhaktivedanta Swami Prabhupada. 1966. Chaitanya Charitamrta lecture. New York.)

Previously when they appeared They did so swith and for a set purpose. Even prior to their appearance in this world Their clear task was already set out. Actually They were not of this world, but are spiritual beings empowered by the Supreme Personality of Godhead to come to this world to fulfil His mission. As we know Lord Buddha came to stop the people from their animal slaughter and to teach the compassionate path. Their appearance in this world was not of some sectarian, conquestrian mission unlike some of their latter day "followers". They appeared at a particular place at a particular time and under specific circumstances that allowed the people of the day to accept their mission as meaningful. It was part of the overall plan to re-instill and spread God consciousness, to the masses who were/are in so much need of it.

From SRI BHAVISHYA PURANA. Pratisarga parva, Chaturyuga Khanda Dvitiyadhyayah, 19th Chapter. (text 17-21 onwards).

"Ruling over the Aryans was a king called Salivahana, the grandson of Vikramaditya, who occupied the throne of his father. He defeated the Sakas who were very difficult to subdue, the Cinas, the people from Tittiri and Bahikaus who could assume any form at will. He also defeated the people from Rome and the descendants of Khuru, who were deceitful and wicked. He punished them severely and took their wealth. Salivahana thus established the boundaries dividing the separate countries of the Mlecchas and the Aryans. In this way Sindusthan came to to be known as the greatest country. That personality appointed the abode of the Mlecchas beyond the Sindhu river and to the west."

ekadä tu çakädhéço
himatuìgm samäyayau
hüëadeçasya madhye vai
giristhaà puruñam çubham
dadarça balabännäjä
gauräìgaà çvetavastrakam

"Once upon a time the subduer of the Sakas went towards Himatunga and in the middle of the Huna country (Hunadesh - the area near Manasa Sarovara or Kailash mountain in Western Tibet), the powerful king saw an auspicious man who was living on a mountain. The man's complexion was golden and his clothes were white." (Bhaviñya Purana 19.22)