The passage
      v32-33. The passage opens with a recurring statement; "No one knows" when the coming of the Son of Man will take place. Jesus is not trying to define the limits of his understanding, but rather emphasize the fact that it is not possible to calculate the day of his coming. Vigilance must be our way of life, rather than calculation. The day Jesus is referring to is the day when we "will see the Son of Man coming in the clouds with great power and glory", v26. This is the day when he is received by the Ancient of Days and begins his eternal heavenly reign, Dan.7:13. This day is a day of judgment and the destruction of Jerusalem in 70AD serves as a paradigm of this day and thus of the last day. The people of Jeremiah's day were looking forward to the great day of the Lord's coming and failed to listen to his warning that the coming of the Lord is not always good news, for it is a coming in judgment. That day will concern the people of God, not just rebellious humanity. Will we be found wanting in that day? Will we stand condemned as have his people in the past? Be vigilant therefore, be on your guard, be alert, be prepared.
      v34-36. Jesus now gives a short teaching parable to explain the thrust of his exhortation. The parable pictures the application of vigilance. Being on guard, being alert, watching, is not just describing expectant waiting, but rather standing ready and prepared for the master's return. The master leaves his house in the care of his servants. Each has their assigned task which is to be faithfully executed. The door-keeper is to keep watch, waiting to open the door at the master's return. The master can return at any time, so there is no possibility for safe-slacking. He can return at any time during the four watches of the night. If he comes unexpectedly, don't be found sleeping. So, the point of the parable is "watch" - be prepared for the Master's return.
      v37. The final verse widens the exhortation to include the church rather than just the immediate disciples. We must all be prepared for the coming Son of Man.

Be prepared!
      The second coming of Christ is a forceful incentive for faithful discipleship. The day will come when Jesus will return and what will he find? Will he find us asleep? So it is essential for us to "be on guard! be alert! watch!" A phrase like "be prepared" probably sums up the meaning of Jesus' words here, but be prepared in what sense? It's very easy to have a stab in the dark on this subject, but there is a principle which covers our lack of information in this passage. We must always interpret scripture from scripture. A disciple's faithfulness is determined by their faith in Christ. It is by grace we are saved through faith and not by works so that no one can boast, Eph.2:9. So, our preparation involves a constant reliance of Christ for salvation. Beware that nothing leads us from a total reliance on faith in Christ for our standing and progress as a believer.
      Does an exhortation for an ongoing reliance on Jesus imply that a believer could lose their salvation? In Reformed churches (ie. Calvinist in theology) there is a simple answer to this question, "once saved, always saved". Mind you, there is little security in this view, for if a person does "fall away" from following Christ, the usual line given is, "Oh well! it just shows they were never really saved in the first place." In the end, knowing we are one of God's elect (chosen, predestined for salvation by a sovereign determination of the will of God) can only be evidenced by never turning our back on Christ. A strict Calvinist may never be able to lose their salvation, but then they can never be sure they are saved.
      The answer to the question has more to do with the nature of faith. God's sovereign choice is primarily exhibited in his choosing the method of salvation. "It is not ... dependent on man's desire or effort, but on God's mercy." God's gift to humanity is a "righteousness for everyone who believes." We stand perfected in the sight of God and thus eternally secure, "by grace though faith." In simple terms then, we cannot lose our salvation while we place ourselves under the mercy of God and rest on his forgiveness freely given in Christ.
      If it is true that God's sovereign will enacts the method of salvation rather than selecting individuals for salvation, then in theory a believer can abandon their faith. Yet, Jesus' prophetic warning serves to empower perseverance. Once we come under the mercy of God, we find that the indwelling Spirit of Christ carries us toward that dreadful day. As long as we place ourselves under the mercy of God we will never lose our salvation and that mercy, of itself, has the power to hold us firm till that great day.

v32
      hJmeraV ekeinhV "that day" - this is an Old Testament technical term used for the day of divine judgment. In this setting it refers to the destruction of Jerusalem, and by implication, the parousia. The addition of the "hour" emphasizes the New Testament theme of the unexpected and sudden coming of the Son of man.
      oiden (oida) perf. "knows" - The clarity of "no one knows" should put an end to predictive speculation, although there are still many believers who enjoy this fruitless pastime. Given that not even "the Son" knows the date we are best to leave it as an unknown.
      oJ uiJoV "the Son" - Some commentators regard this phrase as an addition to the text, given that Jesus would surely know the time of his return. The problem is, other than the Arian heresy which emphasized the humanity of Jesus and which is too late to influence the transmission of this text, there is no good reason why it would have been added.

v33
      agrupneite (agrupnew) imp. "be alert!" - be wakeful, alert, vigilant.... As opposed to sleepy. The question is, of course, in what sense is the believer to be alert, on the lookout? The best guess is that being "on guard" and "alert", "vigilant", means being prepared. We must be prepared for an unexpected and sudden return of Christ. Of course, we must then ask in what sense should we be prepared? The sample sermon takes a particular line, namely faith, but there are numerous other suggestions, usually in the terms of "faithfulness".

v34
      douV (didwmi) aor. part. "puts" - having given. The participle, as with "having left", is adjectival, modifying "man". He gives authority to the slaves; "gives the management to his servants", Weymouth.
      tw/ qurwrw/ (oV) "the one at the door" - the doorkeeper. This person guarded the entrance of the courtyard to a wealthy home or combined homes.
      iJna + subj. "to [keep watch]" - that [he should keep watch, be alert]. This construction here forms a dependent statement of comanding. The doorkeeper is to keep watch. "Commands the doorkeeper to be on the watch", NRSV.

v35
      grhgoreite pres. imp. act. "[So] you also must keep watch" - watch [therefore]. Like the guard we must keep watch (for the coming of a thief or the return of the master. Note the echoes of a number of end-time parables in this illustration), cf. v37. We must be prepared for the coming of the Son of Man. The problem is defining what Jesus means by being watchful, by being prepared. As noted above, many commentators argue that Jesus is calling for "faithful service", active watchfulness, rather than passive waiting, "in Mark's view particularly, the responsibility of the world wide promulgation of the gospel", Anderson. Given the dire warnings against "sleeping", if we adopt the faithfulness tact we end up with a justification and/or sanctification by works scenario. Salvation is by grace through faith and therefore watchfulness, preparedness, must necessarily be a reliance on this one and only means of salvation, namely the grace of God through faith in Christ. In simple terms, we must not take our eyes off Jesus. One easy way for a believer to get into "sleeping" is to start thinking that their faithful behavior secures their standing in the sight of God and/or progresses their Christian life. cf. Gal.3:1-5.
      Note the identification of the four Roman watches of the night.