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Sach Khand is a term used in Sikhism to denote an individual's union with God.
Guru Nanak, the founder of Sikhism, has described a hierarchy of five spiritual levels in the Japji Sahib. The first level is the level of of duty where one acts and performs one's duty. If these duties are performed in a sincere and honest manner, then one enters the second spiritual level called Gian Khand which is the level of knowledge. Here one may obtain knowledge about God and the Universe. One may recognize the omnipotence of God, the vastness of His creation, and the limitations of human endeavor. One may then recognize that there is a purpose behind God's creation at which point of time one enters the third spiritual level called Saram Khand. At this level, one's mind and understanding are purified, and one attempts to perform actions in accordance with the teachings of the Guru. The actions performed at the third level may result in one entering the fourth level, called Karam Khand. At this level one may develop spiritual powers and obtain divine grace. The fifth and ultimate level, called Sach Khand, may only be entered with the grace of God. At this level one may unite with God.
Many Sikhs conceptualize Sach Khand not as a mystical state transcending death, but as a "heavenly abode"—a place where one's spirit goes after death.
References
^ Mansukhani, Gobind Singh (1977). Introduction to Sikhism. Hemkunt Press. p. 71.
McLeod, W.H. (2005). Historical Dictionary of Sikhism (2nd ed). Scarecrow Press. p. 175.