In plain words
Guru Viṣṇuḥ: what is the work Viṣṇu does? Merely because Brahmā has created it, a thing cannot grow. Today, merely because we plant a sapling in the ground, it does not grow into a tree. Only when we build a basin round the sapling we have planted, water it, put manure on it, put a fence round it to protect it, and also take part in many ways in the work of making it grow, does it become a tree. In the same way, it is of no use if gurus merely give a Name, lay down a discipline and tell you to keep following it. Only when he takes the place of Viṣṇu in his turn and puts fitting care into looking after the nourishing strength it needs and the work fit for its growth as well, is there ground for saying Guruḥ Viṣṇuḥ. Next, Gurudevo Maheśvaraḥ. If you ask what work Maheśvara does, the meaning is: bringing about laya. Many people are in the habit of giving many kinds of meaning for laya. Many people do say that it is destroying, or demolishing in some way, or making name and form cease in the pralaya. But this is not the right meaning of laya. Laya means merging. “Līyate gamyate yiti liṅgaḥ,” they have said. That is, just as it is Maheśvara's duty, His karma, to make the effort to bring a thing back to the very abode from which it set out, so too, when a guru sets about the effort to bring his disciple, a human being, into the goal of the Ātma, in keeping with the feeling of the Ātma and again in keeping with the abode of the Ātma, we may give that guru, who belongs to this Prakṛti, a meaning equal to Maheśvara as well. That is, to provide the protection that makes the Name he has given grow, to ripen in this growth the fruit called his own Ānanda, to have him eat that fruit, and to make the very effort fit to bring into their hearts the essence, of the nature of nectar, that sprang from that seed: this Guru Brahmā, Guru Viṣṇu, Gurudevo Maheśvara, these three cannot be separate.