If he sleep, he shall do well - That is, if he sleep only, etc. Though the word sleep frequently meant death, (see Acts 7:60; 1 Corinthians 11:30; 1 Corinthians 15:18, 1 Corinthians 15:20), yet, as it was an ambiguous term, the disciples appear here to have mistaken its meaning. Because, in certain acute disorders, the composing the patient to rest was a favorable sign; therefore the words, If he sleep, he shall do well, or recover, became a proverbial forth of speech among the Jews. In most diseases, sleep is a very favorable prognostic: hence that saying of Menander: -

Ὑπνος δε πασης εϚιν ὑγιεια νοσου.

Sleep is a remedy for every disease.

See Grotius here. The meaning of the disciples seems to have been this: There can be no need for thee to go into Judea to awake our friend Lazarus; he will awake time enough, and his very sleep is a presage of his recovery: therefore do not hazard thy life by going.

Matthew 9:24 He said, "Leave; for the girl has not died, but is asleep." And they began laughing at Him.

Luke 8:52 Now they were all weeping and lamenting for her; but He said, "Stop weeping, for she has not died, but is asleep."

June 22 Evening
Behold how he loved.--JOHN 11:36. He died for all.--Greater love hath no man than this, that a man lay down his life for his friends. He . . . liveth to make intercession for them.--I go to prepare a place for you. I will come again, and receive you unto myself that where I am, there ye may be also.--Father, I will that they whom thou hast given me, be with me where I am.--Having loved his own which were in the world, he loved them unto the end. We love him, because he first loved loved us.--The …
Anonymous—Daily Light on the Daily Path

A Mystery! Saints Sorrowing and Jesus Glad!
Jesus is talking of the death of His friend, let us listen to His words; perhaps we may find the key to His actions in the words of His lips. How surprising! He does not say, "I regret that I have tarried so long." He does not say, "I ought to have hastened, but even now it is not too late." Hear, and marvel! Wonder of wonders, He says, "I am glad that I was not there." Glad! the word is out of place? Lazarus, by this time, stinketh in his tomb,and here is the Saviour glad! Martha and Mary are weeping …
Charles Haddon Spurgeon—Spurgeon's Sermons Volume 10: 1864

Beloved, and yet Afflicted
We need not be astonished that the man whom the Lord loves is sick, for he is only a man. The love of Jesus does not separate us from the common necessities and infirmities of human life. Men of God are still men. The covenant of grace is not a charter of exemption from consumption, or rheumatism, or asthma. The bodily ills, which come upon us because of our flesh, will attend us to the tomb, for Paul saith, "we that are in this body do groan." Those whom the Lord loves are the more likely to be …
Charles Haddon Spurgeon—Spurgeon's Sermons Volume 26: 1880