1) One should wake up from sleep at the hour known as the Brahma Muhurta and then think of both religion and profit.
2) The Rishis, in consequence of their adoring the two twilights with great regularity succeeded in attaining to longevity. Hence, one should, restraining speech, say one's prayers regularly at the two twilights. As regards those Brahmanas that do not say their prayers at the two twilights, a righteous king should set them to accomplish such acts as are ordained for the Sudras.
3) One should not, O king, sleep at the evening twilight. Nor should one study at such an hour for acquiring any branch of knowledge.
4) They who sleep at any of the twilights, or at nightfall or who go to sleep in a state of impurity, have their lives shortened.
From the above statements, it is clear that one should neither sleep nor talk during both twilights. One should not study during evening twilight.
My doubt is whether a person can study for acquiring knowledge during morning twilight? If no, which slokha is explaining that restriction.