SB 4.24.15

yad uktaṁ pathi dṛṣṭena
 giriśena prasīdatā
tad dhyāyanto japantaś ca
 pūjayantaś ca saṁyatāḥ
Word for word: 
yat — that; uktam — said; pathi — on the way; dṛṣṭena — while meeting; giriśena — by Lord Śiva; prasīdatā — being very much satisfied; tat — that; dhyāyantaḥ — meditating; japantaḥ ca — chanting also; pūjayantaḥ ca — worshiping also; saṁyatāḥ — with great control.
Translation: 
When all the sons of Prācīnabarhi left home to execute austerities, they met Lord Śiva, who, out of great mercy, instructed them about the Absolute Truth. All the sons of Prācīnabarhi meditated upon the instructions, chanting and worshiping them with great care and attention.
Purport: 

It is clear that to perform austerities or penances or, for that matter, any form of devotional service, one has to be guided by a spiritual master. Here it is clearly stated that the ten sons of Mahārāja Prācīnabarhi were favored by the appearance of Lord Śiva, who, out of great kindness, gave them instructions regarding the execution of austerities. Lord Śiva actually became the spiritual master of the ten sons, and in turn his disciples took his words so seriously that simply by meditating upon his instructions (dhyāyantaḥ) they became perfect. This is the secret of success. After being initiated and receiving the orders of the spiritual master, the disciple should unhesitatingly think about the instructions or orders of the spiritual master and should not allow himself to be disturbed by anything else. This is also the verdict of Śrīla Viśvanātha Cakravartī Ṭhākura, who, while explaining the verse of Bhagavad-gītā beginning vyavasāyātmikā buddhir ekeha kuru-nandana (Bg. 2.41), points out that the order of the spiritual master is the life substance of the disciple. The disciple should not consider whether he is going back home, back to Godhead; his first business should be to execute the order of his spiritual master. Thus a disciple should always meditate on the order of the spiritual master, and that is perfectional meditation. Not only should he meditate upon that order, but he should find out the means by which he can perfectly worship and execute it.