The disciples respond to Jesus - "Lately the Jews sought to stone You" (11:8; cf. 10:31). This plan seems unwise and dangerous to them. However, they were not cowards. This appears to be their only explicit effort to dissuade Him (cf. 11:16).
Jesus asked - "Are there not twelve hours in the day?" Jesus' purpose here was not to discuss the number of hours of daylight received each day but rather to reiterate that His time to die had not yet come (cf. 7:6; 9:4).
"If anyone walks in the day, he does not stumble, because he sees the light of this world" - Jesus now states another physical truth pertaining to light, and He makes a spiritual application. He is declaring the fact that as long as He walks faithfully (i.e., "in the light" - I John 1:7), then His work would be accomplished regardless of the evil intentions of the Jews. He would not die before His time had come, and thus there was no need for Him to fear. Likewise, today, if any man is performing the will of God then he has no reason to fear the sinister plans of Satan or the wicked schemes of men. As long as he walks in the light, he will not stumble!
"But if one walks in the night, he stumbles, because the light is not in him" (John 11:11). This too is true both physically and spiritually. If one is not doing the will of God then he is walking in darkness and will stumble spiritually. It was certainly the will of God for Jesus to raise Lazarus from the dead. Thus, He would not be persuaded to turn away from God's will and into the "darkness" out of fear for His life.
"Lazarus sleeps, but I go that I may wake him up" (cf. Luke 8:52). There was never any doubt in Jesus' mind as to what He would do. He would go and "wake up" Lazarus' physical body from its "sleep" by reuniting it with his spirit (cf. James 2:26). The Scriptures often refer to death as sleeping. This is likely the case because the physical body looks as if it is sleeping when deceased. However, this is not to say that one's spirit becomes unconscious at death, as Luke 16:19ff easily refutes. Some have also suggested that death is referred to as sleep to reiterate the idea that physical death is only temporary (cf. John 5:28,29).
The disciples respond - "Lord, if he sleeps he will get well" (John 11:12). They misunderstood that Jesus intended to resurrect Lazarus, probably because they didn't think that he had died from his illness. There is probably also the implication here that since they believe Lazarus will recover, then there is no need for them to go to the dangerous region of Judea at this time.
Jesus then drops His figurative language and plainly states - "Lazarus is dead." Thus, Lazarus wouldn't just "wake up" on his own as if from a long sleep related to recovery from a serious illness.
John 11:15 records Jesus' gladness that He wasn't in Bethany while Lazarus was sick because then He would have felt compelled to heal him. In so doing He would have lost the opportunity of presenting His disciples and the world with one of the greatest proofs of His deity and Messiahship.
Thomas then adequately expresses the gloom that has probably settled over the apostles - "Let us also go, that we may die with Him." He seemed to see only one possible outcome of Jesus going to Bethany--namely, death! So, although Thomas didn't understand or simply lacked faith in the assurance Jesus expressed in 11:9,10,15, he should be credited for willingly choosing death with Jesus rather than life without Him.