In the Skanda Purana it is advised that a devotee follow the past acaryas and saintly persons because by such following one can achieve the desired results, with no chance of lamenting or being baffled in his progress.
In the scripture known as Brahma-yamala it is stated as follows: "If someone wants to pose himself as a great devotee without following the authorities of the revealed scriptures, then his activities will never help him to make progress in devotional service. Instead, he will simply create disturbances for the sincere students of devotional service." Those who do not strictly follow the principles of revealed scriptures are generally called sahajiya, those who have imagined everything to be cheap, and who have their own concocted ideas, and who do not follow the scriptural injunctions. Such persons are simply creating disturbances in the discharge of devotional service.
In this connection, an objection may be raised by those who are not in devotional service and who do not care for the revealed scriptures. An example of this is seen in Buddhist philosophy. Lord Buddha appeared in the family of a high-grade ksatriya king, but his philosophy was not in accord with the Vedic conclusions and therefore was rejected. Under the patronage of a Hindu king, Maharaj Asoka, the Buddhist religion was spread all over India and the adjoining countries. However, after the appearance of the great stalwart teacher, Sankaracarya, this Buddhism was driven out beyond the border of India.
The Buddhists or other religionists who do not care for revealed scriptures sometimes say that there are many devotees of Lord Buddha who show devotional service to Lord Buddha and who therefore should be considered devotees. In answer to this argument, Rupa Gosvami says that the followers of Buddha cannot be accepted as devotees. Although Lord Buddha is accepted as an incarnation of Krsna, the followers of such incarnations are not very advanced in their knowledge of the Vedas. To study the Vedas means to come to the conclusion of the supremacy of the Personality of Godhead. Therefore any religious principle which denies the supremacy of the Personality of Godhead is not accepted and is called atheism. Atheism means defying the authority of the Vedas and decrying the great acaryas who teach Vedic scriptures for the benefit of the people in general.
Lord Buddha is accepted as an incarnation of Krsna in the Srimad-Bhagavatam, but in the same Srimad-Bhagavatam it is stated that Lord Buddha appeared in order to bewilder the atheist class of men. Therefore his philosophy is meant for bewildering the atheists and should not be accepted. If someone asks, "Why should Krsna propagate atheistic principles?" the answer is that it was the desire of the Supreme Personality of Godhead to end the violence which was then being committed in the name of the Vedas. The so-called religionists were falsely using the Vedas to justify such violent acts as meat-eating, and Lord Buddha came to lead the fallen people away from such a false interpretation of the Vedas. Also, for the atheist class, Lord Buddha preached atheism so that they would follow him and thus be tricked into devotional service to Lord Buddha, or Krsna.

Link to this page:

If you Love Me Distribute My Books -- Srila Prabhupada