Vivekachudamani 8

ato vimuktyai prayateta vidvan
sannyastabahyarthasukhasprhah san |
santam mahantam samupetya desikam
tenopadistarthasamahitatma (Vivekachudamani 8)

Therefore, the learned seeker who is striving to gain this liberation and who has renounced all his desires for pleasures in the external sense-objects, should duly approach a good and generous Master and must live attuned to the true significances of the words of the Master.

Purport

 Within the material world one is certainly attracted to becoming a great intellectual, a powerful politician, the loving father of many beautiful and affectionate little children, a most honored welfare worker or a highly admired and successful businessman. But none of these material positions have a permanent basis, nor do they afford permanent liberation, because they are all based on the primary misunderstanding by which one identifies himself with the material body.

 Moksha or liberation reward is an eternal life of bliss and knowledge in the kingdom of God, where there is no punishment. The kingdom of God is Vaikuṇṭha, or unconditional pleasure. There is no punishment in the spiritual world; it is a place of ever-increasing pleasure by serving the Lord eternally.

 To achieve liberation we need a bona fide spiritual master is one who is expert in all of these subject matters, not by his personal imagination or speculation but by mature understanding of the authorized Vedic literatures, which are the literary manifestation of the causeless mercy of God. The Lord says in Bhagavad-gītā (9.3).

aśraddadhānāḥ puruṣā
dharmasyāsya parantapa
aprāpya māḿ nivartante
mṛtyu-saḿsāra-vartmani

 "Those who are not faithful on the path of devotional service cannot attain Me, O conqueror of foes, but return to birth and death in this material world."

Therefore the spiritual master must awaken the disciple to the eternal existence of devotional service. The example may be given that in the early morning a mother may enter her child's room to wake him up so that he can attend school. The child does not want to get up, but the loving mother forces him to get up and sends him off to school to be educated. Similarly, the bona fide spiritual master awakens the sleeping soul and sends him to the gurukula, or the āśrama of the spiritual master, where he can be trained in perfect knowledge.

In Bhagavad-gītā (9.13) it is said,
mahātmānas tu māḿ pārtha
daivīḿ prakṛtim āśritāḥ
bhajanty ananya-manaso
jñātvā bhūtādim avyayam

 Those who are actually great souls have surrendered to the internal potency of the Lord and can similarly connect others to the internal pleasure-giving potency. A mahātmā is described in Bhagavad-gītā as follows: vāsudevaḥ sarvam iti sa mahātmā sudurlabhaḥ [Bg. 7.19]. "He knows Me to be the cause of all causes and all that is. Such a great soul is very rare." It is to such a spiritual master, who has reached the mature understanding that Vāsudeva is everything, that one must surrender. According to Śrī Nārada Muni, yo vidvān sa gurur hariḥ: such a great soul is to be considered the external manifestation of Kṛṣṇa Himself. Kṛṣṇa states this also:

ācāryaḿ māḿ vijānīyān
nāvamanyeta karhicit
na martya-buddhyāsūyeta
sarva-devamayo guruḥ

"One should know the ācārya to be Myself and never disrespect him in any way. One should not envy him, thinking him an ordinary man, for he is the representative of all the devas." (Bhāg. 11.17.27)