Islams prespective on ancestor worshipping.

??The worship of ancestors:

During his life, Prophet Mohammad (PBUH) denounced every form of Shirk, the act of associating anything or anybody with God Almighty in His attributes and powers, a sin considered unforgivable in Islamic theology.

Indeed, Allah does not forgive association with Him, but He forgives what is less than that for whom He wills. And he who associates others with Allah has certainly gone far astray. (Quran 4:116)

 If not repented during the sinner’s earthly life. Because ancestor worship and one's association with their graves was a common religious practice in pre-Islamic Arabia, Prophet Mohammad, even on his deathbed, warned Muslims not to imitate Jews and Christians who earlier had venerated the graves of their prophets and saints (Sahih Muslim, Mishkat). 

But before we proceed with our inquiry into this important topic, let us first review a few terms, especially in the context of ancient cultures. By definition ancestor worship is the adoration or payment of homage to a deceased parent or ancestor. In this type of worship, usually reserved for deities, a devotee claimed spiritual relationship to the deceased. One can easily find several examples of deification of ancestors in Indian, Mesopotamian, and Egyptian mythologies. In such cultures it is quite conceivable that even a “living” ruler could easily proclaim divinity without much problem, as was done by the Pharaoh saying to Moses and his own courtiers.
"And said, 'I am your most exalted lord'".(Quran 79:24) 

Grave worship, much like ancestor worship, involves adoration of the deceased with a belief that certain departed spirits must be fed or honored. With this, they could become channels of information with the spiritual world (necromancy) and intercessors with God Almighty. Excessive reverence and love for the deceased and a belief in afterlife in the worldly grave was apparently the reason behind such practices. It is important to realize that throughout human history idols were actually made in remembrance of those departed “saintly” souls. To make us understand the Quranic verse in which the adversaries of Prophet Noah said to their fellow compatriots,
'And said, 'Never leave your gods and never leave Wadd or Suwa' or Yaghuth and Ya'uq and Nasr'.(71:23)
  
Abdullah Bin Abbas (RA) explained that they were the saintly men who followed Noah’s monotheistic religion and when they died, people associated themselves with their dead cult, made idols in their resemblance, and started worshipping them (Sahih Bukhari; Commentary of Chapter Noah from the Holy Quran).

#Allah alone regulates the affairs of the universe such as giving and taking life, sending the rain down, giving sustenance, alternating the night and the day, giving honour to whom He wishes and humble whom He wishes 

Setting up intermediaries between a person and #Allah is Kufr (disbelief):
calling upon them and seeking their intercession and depending upon them. Those who do this are taking "associates" with Allah and this is #Shirk.

In Quran 

Quote from the Holy Qur'an: An-Nisaa (4:48)
Indeed, Allah does not forgive association with Him, but He forgives what is less than that for whom He wills. And he who associates others with Allah has certainly fabricated a tremendous sin.