In plain words
Bhakti itself, at the lotus feet of the Sadguru, is the path that brings you swiftly to Mukti; firm restraint of the senses and the mind, that alone will show you God, who dwells in the heart.
Embodiments of the divine Ātma!
Steady Bhakti at the guru's feet, detachment from saṃsāra, mastery of the senses, the mind brought under control: to the person who has achieved these four, the divinity that dwells in the seat of his own heart may be revealed. With this purpose Śaṅkara gave this very last śloka, and set out to make his way back from Kāśī.
He taught only that there must be steady Bhakti at the guru's feet; but first of all we must also consider what kind of person the guru ought to be. Kovaguru hitopadeśaḥ: that is, the one who teaches what is for our good, who develops a person's religious nature, makes his understanding blossom, has him perform the karmas the śāstras approve, and gives the teaching fit to light the flame of the Ātma in the seat of the heart, may be called the guru. Now we must also reflect a little on the inner meaning held in these two syllables, gu-ru. The syllable gu means darkness, and the syllable ru means its removal: this too is one meaning of it. That is, with the purpose that the darkness called Ajñāna may be dispelled by the light called Jñāna, the guru makes the effort fit to dispel the Ajñāna that has covered us, to give us the principle of Prajñāna, and to merge us in his own radiant Ātma-principle.