Srimad Bhagavatam Canto 11, Chapter 31, Text 13

SB 11.31.13

tathapy asesa-sthiti-sambhavapyayesv
 ananya-hetur yad asesa-sakti-dhrk
naicchat pranetum vapur atra sesitam
 martyena kim sva-stha-gatim pradarsayan
Although Lord Krsna, being the possessor of infinite powers, is the only cause of the creation, maintenance and destruction of innumerable living beings, He simply did not desire to keep His body in this world any longer. Thus He revealed the destination of those fixed in the self and demonstrated that this mortal world is of no intrinsic value.
Although Lord Krsna descended to this world to save the fallen souls, He did not want to encourage people in the future to loiter here unnecessarily. In other words, as soon as possible one should perfect one’s Krsna consciousness and go back home, back to Godhead. If Lord Krsna had remained longer on the earth, He would have unnecessarily increased the prestige of the material world.
As stated by Sri Uddhava in Srimad-Bhagavatam (3.2.11), adayantar adhad yas tu sva-bimbam loka-locanam: “Lord Sri Krsna, who manifested His eternal form before the vision of all on the earth, performed His disappearance by removing His form from the sight of those who are unable to see Him [as He is] due to not executing the required penance.” Uddhava also states in the Bhagavatam (3.2.10):
devasya mayaya sprsta
 ye canyad-asad-asritah
bhramyate dhir na tad-vakyair
 atmany uptatmano harau
“Under no circumstances can the words of persons bewildered by the illusory energy of the Lord deviate the intelligence of those who are completely surrendered souls.” One who follows the Vaisnava authorities in his attempt to understand Lord Krsna’s transcendental disappearance easily appreciates that the Lord is the omnipotent Personality of Godhead and that His spiritual body is identical with His eternal spiritual potency.
Srimad Bhagavatam Canto 11, Chapter 31, Text 12
Srimad Bhagavatam Canto 11, Chapter 31, Text 14