As with many Proverbs, Solomon sets this one up with a very general application at the beginning.  “Anyone” who meets the condition that he lays out will reap the benefit he describes.  “Keep” speaks of the act of guarding, in a good sense (to protect, maintain, obey, etc.).  It is obviously to be seen here it the farming (or private gardening) context.  We ask the question “keeps” what?  Seems clear that solomon’s intention is to tell us that the one who tends properly and fully to the fig tree will reap the pleasure of good and tasty fruit; as the purpose of the tree is to begin with.  It seems sure that this would be an obvious conclusion to draw, to see when one would think about the matter.
     “So” means that this second phrase is to be seen as speaking in the same generalized fashion.  In the same fashion as attention to the gardening necessities of the Fig Tree yields wonderful fruit; so also the servants’ “waiting” on his Master will yield his (the servants’) being honored.  “Waiting” speaks of the act of hedging about (as with thorns), i.e. namely guarding; generally speaking of the act of protecting, attending to, etc.  In a non-literal sense it can speak of being circumspect, taking heed (to self), keeping yourself), preserving to an end.
     Solomon’s point seems to be that the servant pays due and careful attention to his Master reaps honor due such attention from that Master.
 
Interpretation. - The fig tree in Judaea is so abundant, that for its fruit to fail was a severe judgment (Joel 1:6, 7; Hab. 3:17). The diligent husbandman would have his reward in being partaker of its fruits (2 Tim. 2:6). Even so, the faithful servant who “guards or observes” his master, shall reap the fruits of his diligence in honor, confidence, reward, advancement - probably, if a slave, in his liberation. And this applies to the service of the heavenly even more than of an earthly master.
 
Illustrations.

• Eliezer, Deborah, Joseph, the steward, the nurse, the slave, all attained to honor through faithful service (Gen. 24:12–15, 45, 50; 35:8; 37; 39; 41).
• Elisha, who had persevered in watchful attendance on his master, was rewarded by a double portion of his spirit.
• The centurion’s servant, and the devout soldier who waited on Cornelius continually, had each his reward in the attachment and good offices of those they served (Luke 7:2, 8; Acts 10:7, 24, 48).
• Luke (whose day is sometimes kept in the various sides of the church) became St. Paul’s loving and beloved attendant even to the end of his afflictions (2 Tim. 4:11), and, in return, profited by his art of healing souls, derived from him aid in his immortal book as an Evangelist, had the privilege of constant communion with his spirit, and was honored in his own lifetime, as now, by his praise being in the Gospel, and by becoming (whether a slave or not) “the Lord’s free man” (1 Cor. 7:22).

 
Application. - Never let the humblest service be despised, for, if faithfully rendered, it shall have its reward, if not at the hands of man, yet of God. A good master will thoroughly appreciate and not forget to acknowledge the trusty watchful care of an attached servant. He will employ him confidentially, increase his wages, advance him to honor. Or if some earthly masters are strangely neglectful of what is due to their servants, not so the Master Christians delight to serve. Himself a pattern servant (of His own free will) to His Father, “faithful to Him that appointed Him” (Heb. 3:2), and therefore “highly exalted” (Phil. 2:9), there is no duty rendered Him on our part which He sees not, acknowledges not, crowns not. He demands no work but what is due; sends no one a warfare on his own charges; is large in His promises; smiles upon active fidelity. The most ordinary calling is a service to Him, however mean. The common task of daily life done “as unto the Lord” is the best proof of our love. From Him will our fruits be found (Hos. 14:8).

Psalm 6:8
 - Charles Spurgeon

"The LORD has heard the voice of my weeping!" 

     Is there a voice in weeping? Does weeping speak? 
     In what language does it utter its meaning? Why, in that universal tongue which is known and understood in all the earth, and even in Heaven above. When a man weeps, whether he is a Jew or Gentile, Barbarian, Scythian, bond or free--it has the same meaning in it. 
     Weeping is the eloquence of sorrow. It is a wordless orator, needing no interpreter, but understood by all. 
Is it not sweet to believe that our tears are understood by God, even when words fail? 
Let us learn to think of tears as liquid prayers, and of weeping as a constant dropping of importunate intercession which will surely trickle its way into the very heart of divine mercy. 
     My God, I will "weep" when I cannot plead--for You hear the voice of my weeping.
CH Spurgeon

     True believers will heed the Good Shepherd’s voice and reject the overtures of false shepherds. Submitting to the authority of Christ is fundamental to the life of faith: “If you love Me, you will keep My commandments” (John 14:15).   

     The Jebusites still held a stronghold in the heart of the country, never having been dislodged. Just so, there are 'Jebusites' in every Christian heart!
     In every heart, there are little 'Jebusite strongholds', which it seems impossible for us to conquer. Sometimes it is a secret sin which lives on, unconquered, amid the general holiness of a life. Sometimes it is a remnant of the old nature--such as pride, worldliness, selfishness, lust, or bitterness. There are many other such citadels of evil, which rear their proud towers and defy conquest.
     "We all have our faults!" we say, and under this cloak we manage to tuck away a large number of dear idols that we do not want to give up!
     ​We ought to give attention to these unsubdued parts of our life--that every thought, feeling, and temper may be brought into subjection to Christ. It is perilous to leave even one such unconquered stronghold in our heart!