Who is the true guru? Guru Nanak explains in this poem:
Gauree, First Mehl:
Gur Parsaadi boojh lay hoye nibera
By Guru's Grace, one comes to understand, and then, the account is settled.
In each and every heart is the Name of the Immaculate Lord; He is my Lord and Master. ||1||
Without the Word of the Guru's Shabad, no one is emancipated. See this, and reflect upon it.
Even though you may perform hundreds of thousands of rituals, without the Guru, there is only darkness. ||1||Pause||
What can you say, to one who is blind and without wisdom?
Without the Guru, the Path cannot be seen. How can anyone proceed? ||2||
He calls the counterfeit genuine, and does not know the value of the genuine.
The blind man is known as an appraiser; this Dark Age of Kali Yuga is so strange! ||3||
The sleeper is said to be awake, and those who are awake are like sleepers.
The living are said to be dead, and no one mourns for those who have died. ||4||
One who is coming is said to be going, and one who is gone is said to have come.
That which belongs to others, he calls his own, but he has no liking for that which is his. ||5||
That which is sweet is said to be bitter, and the bitter is said to be sweet.
One who is imbued with the Lord's Love is slandered - his is what I have seen in this Dark Age of Kali Yuga. ||6||
He serves the maid, and does not see his Lord and Master.
Churning the water in the pond, no butter is produced. ||7||
One who understands the meaning of this verse is my Guru.
O Nanak, one who knows his own self, is infinite and incomparable. ||8||
He Himself is All-pervading; He Himself misleads the people.
By Guru's Grace, one comes to understand, that God is contained in all. ||9||2||18||