For a beginner in the spiritual path, a Guru is necessary. To light a candle, you need a burning candle. An illumined soul alone can enlighten another soul. Some do meditation for some years independently. Later on, they actually feel the necessity for a Guru.
Only the man who has already been to Badrinath will be able to tell you the way. In the case of the spiritual path, it is still more difficult to find your way. The mind will mislead you very often. The Guru will be able to remove pitfalls and obstacles, and lead you along the right path. He will tell you: This road leads you to Moksha (liberation); this one leads to bondage. Without this guidance, you might want to go to Badrinath, but find yourself in Delhi!
The scriptures are like a forest. There are ambiguous passages. There are passages which are apparently contradictory. There are passages which have esoteric meanings, diverse significance, and hidden explanations. There are cross-references. You are in need of a Guru or Preceptor who will explain to you the right meaning, who will remove doubts and ambiguities, who will place before you the essence of the teachings.
A Guru is absolutely necessary for every aspirant in the spiritual path. It is only the Guru who will find out your defects. The nature of egoism is such that you will not be able to find out your own defects. Just as a man cannot see his back, so also he cannot see his own errors. He must live under a Guru for the eradication of his evil qualities and defects.
The aspirant who is under the guidance of a Master or Guru is safe from being led astray. Satsanga or association with the Guru is an armour and fortress to guard you against all temptations and unfavourable forces of the material world.
However, it is important to follow the spiritual instructions of one man only. If you go to several people and follow the instructions of many persons, you will be bewildered. You will be in a dilemma.
From a doctor, you get a prescription. From two doctors, you get consultation. From three doctors, you get your own cremation. Even so, if you have many Gurus, you will be bewildered. You will be at a loss to know what to do.