The Father, who sent Christ into the world, gave him work to do: his general work was, to glorify God upon the earth, 1 Thessalonians 17:4, as by working out the redemption of man, so by revealing his will to the sons of men, and working miracles for the glorifying the name of God. Saith Christ, I have a set time to work in; that is, that which he here calleth day, the time wherein Christ was to live upon the earth. The night cometh, when no man can work; I am not to be here always, there will come a time when I must be absent from the earth, then none of this work can be done. A good argument to persuade every Christian to work while the time of his life lasts, for the night of death will come, when no man can any longer work out his salvation; but as the tree falleth, so it must lie, Ecclesiastes 9:10.
Related Commentaries of John 9:4
John 9:4
4 I must work the works of him that sent me, while it is day: the night cometh, when no man can work.