After being resurrected Jesus appeared "to them over a period of forty days" (Ac 1:30). "The rain fell upon the earth for forty days" (Ge 7:12) as judgment. They spied out the land for "forty days" (Nu 13:25) but then wandered "forty years" (:34) because of their disobedience. Jesus was tested for "forty days" (Ac 1:3). Jonah preached to Nineveh for "forty days" (Jon 3:4) regarding repentance. During this period Jesus "presented himself alive . . . by many convincing proofs" (Ac 1:3). He also spoke of the "kingdom of God" (:3). It is said that the number forty is symbolic of a probationary period. A certain period of time was necessary to make the point that he had indeed risen from the dead. Also, he had some additional instructions for them because he would no longer be present with them in the same way. He had previously prayed, "'I am no longer in the world; and yet they themselves are in the world'" (Jn 17:11).
Jesus had taught before using the symbols of his flesh and blood. The Jews argued, saying, "'How can this man give us His flesh to eat?'" (Jn 6:52). In John 6:53-58 he mentions this eating six times and the drinking four times. His disciples commented, "'This is a difficult statement; who can listen to it?'" (:60). But if they can't comprehend this then Jesus replies, "'What then if you see the Son of Man ascending to where He was before?'" (:62). His point is unless you do this "'you have no life in yourselves'" (:53). Food and drink provide sustenance for life. He instructs that whoever "'believes in him will have eternal life'" (:40). He who obeys "'abides in Me and I in him'" (:56) and "'will live forever'" (:58). He explains, "'I live because of the Father, so he who eats Me, he will also live because of Me'" (:57). "'It is the Spirit who gives life; the flesh profits nothing'" (:63). "'I go to prepare a place for you . . . [and] will come again and receive you to Myself, that where I am, there you may be also'" (Jn 14:2-3). "'I will raise him up on the last day'" (6:54).