Bhagavad Gita, VII: 6-10

On whatever sphere of being the mind of a man may be intent at the time of death, thither he will go.
Therefore meditate always on Me, and fight; if thy mind and thy reason be fixed on Me, to Me shalt thou surely come.
He whose mind does not wander, and who is engaged in constant meditation, attains the Supreme Spirit.
Whoso meditates on the Omniscient, the Ancient, more minute than the atom, yet the Ruler and Upholder of all, Unimaginable, Brilliant like the Sun, Beyond the reach of darkness;
He who leaves the body with mind unmoved and filled with devotion, by the power of his meditation gathering between his eyebrows his whole vital energy, attains the Supreme.