Samuel Logan Brengle emphasizes the necessity of having an undivided heart in the pursuit of soul-winning, arguing that a divided heart cannot effectively lead others to true repentance and a relationship with Jesus. He illustrates that the soul-winner's task is profound, requiring complete dedication and abandonment to God's work, akin to the commitment shown by great figures in history. Brengle warns against distractions and the temptation to retreat, urging that true success in ministry comes from a heart wholly devoted to God. He concludes by affirming that regardless of one's abilities or education, a perfect heart towards God is what He blesses, as seen in the scripture that highlights God's search for those whose hearts are perfect toward Him.

Unite my heart. -- David. He who thinks to succeed in this infinite business of saving souls with a heart that is divided as yet knows nothing as he ought to know concerning the matter. That a man may by personal magnetism, grace of manners, power or persuasiveness of speech, and a certain skill in playing upon the emotions and self-interest of the people, create an excitement that fairly simulates a revival; and yet have a divided heart, I admit; but that he can bring men to a thorough repentance and renunciation of sin, a hearty embrace of the Cross, an affectionate surrender to Jesus as a personal Saviour and Master who requires deep humility and meekness and tender love as the marks of His disciples is hard to be proved. As certainly as like begets like, so certainly will the soul-winner put the mark of his own spirit and consecration upon the people he influences; if he is himself not more than half won to the cause of his lowly Master, he will not more than half win others. His task is the mightiest to which men were ever set. The physical scientist manipulates and changes dead matter, the newspaper man seeks principally to amuse or interest people for the passing hour; the lawyer and politician simply seek to change and mold the opinions of men; but the soul-winner is dealing with fundamentals. His object is not merely to change the opinions and conduct, but to change character; to work a moral revolution in the affections, the dispositions, the wills of men; to turn them from temporal things which they see, to eternal things, which they do not see, from all vices to virtues, from utter selfishness to utter self-sacrifice, and often in spite of all present self-interest, and in the face of the combined opposition of the world, the flesh and the devil. His object is not alone to save them from the guilt and penalty of sin, but from the pollution and the power and the love of sin. Nor is it merely to save men from sin, which is rather a negative work, but to save them into all goodness and love and holiness through a vital and eternal union with Jesus -- a union that gives perpetual vigor and energy and fruitfulness in righteousness to all the powers of the soul, filling it with grace and truth. This is no little work, and can never be the work of a man with a divided heart. It is like turning Niagara Falls back upon its source, or causing the sun and the moon to stand still on Ajalon; it can only be done by God's power, and that power is only fully bestowed upon, and only works freely in and through those whose hearts are perfect toward Him. The soul-winner, then, must once and for all, abandon himself to the Lord and to the Lord's work, and, having put his hand to the plow, must not look back, if he would succeed in this mighty business. He must love his Lord and love his work, and stick to it through all difficulties, perplexities and discouragements, and not be given to change, for there is no discharge in this war. Here it is that many fail; they have not a single eye. They make provisions for retreat. They are double-minded, like an officer I knew, who dabbled in photography till it divided his life and heart, and got him out of the work; like a minister of whom I heard the other day, who reads another man's sermons to his people, while he studies law, saying that when he gets a poor appointment he will fall back on the law and leave the ministry, forgetting Paul's words to Timothy: "No man that warreth entangleth himself with the affairs of this life; that he may please Him that hath chosen him to be a soldier." (2 Tim. 2:4.) By and by such men leave the work God sets them to do, because, as they say, they have not been treated well, when the fact is, their minds being divided, they cease to work well; they no longer give themselves wholly to it, and the people feel a lack of interest and power, hungering souls that look for bread receive a stone, poor sinners, on the road to hell, and possibly on the brink of ruin, go from their cold and heartless services unawakened and unsaved. They lost their grip first on God and then on the crowd, and their superiors, perplexed to know what to do with them, and where to place them, since the people no longer want them, are blamed. But blame others as they will, the blame still lies with themselves. No great work has ever been accomplished without abandonment to it. Michael Angelo said his work was his wife and the statues he made were his children. Edison is so wedded to his work that all other things are forgotten and set aside in the pursuit of his marvelous inventions. Demosthenes, the greatest of ancient orators, if not the greatest of all time, was hissed off the platform at his first appearance. His figure was unprepossessing, and his voice weak and harsh, but he determined to be heard. He devoted himself to his studies, shaved one side of his head lest he should be led into society, and practiced elocution by day and by night. To perfect his enunciation he filled his mouth half-full of pebbles and practiced while climbing a hill; and that he might successfully contend against the thunders of the Athenian mob, he went to the seashore and strengthened his voice by practicing it against the thunder of the waves. Lord Beaconsfield stood for parliament five times, and at last won his seat. When he first attempted to speak he was laughed from the floor but he sat down saying, "You will listen to me yet;" and they did, when, as prime minister of England, he arbitrated the destinies of Europe and crowned Victoria Empress of India. "How long did it take you to prepare that address?" was asked of a great speaker. "All my lifetime in general, and fifteen minutes in particular," he replied. When Benjamin Franklin, as a poor boy, opened a printing-shop, a prosperous competitor said he would drive him out of town. Franklin showed him a piece of black bread from which he dined, and a pail of water from which he drank, and asked if he thought a man who could live on fare like that and work sixteen hours a day could be driven out of town! Who knows the name of that competitor? and who has not heard of Franklin? If men engaged in secular pursuits are thus given up to their work and consumed with their purpose, how much more should the soul-winner be, he who is fighting for righteousness and holiness, for the kingdom of love upon earth, rescuing souls from the power of sin and the danger of eternal burnings? If God has set you to win souls, O my brother, make no provision for the flesh, to fulfill the lusts thereof. Cut the bridge down behind you. Remember Paul's words to Timothy: "Give thyself wholly to them, that thy profiting may appear to all." Let your eye be single, make no plan for retreat, allow no thought of it. Remember Paul's "Woe is me, if I preach not the Gospel." Like Jesus, set your face steadfastly toward your Jerusalem, your cross, your kingdom, your glory, when, having turned many to righteousness, you "shall shine as the stars for ever and ever." (Dan. 12:3.) You may be ignorant and illiterate, your abilities may be very limited, you may have a stammering tongue, and be utterly lacking in culture, but you can have an undivided a perfect heart toward God and the work He has set you to do, and this is more than all culture and all education, all gifts and graces of person and brain. If God has bestowed any of these upon you, see to it that they are sanctified, and that your trust is not in them. But if He has denied them to you, He yet hath called you to the fellowship of His Son, and to His service. Be not dismayed; it is not the perfect head, but the perfect heart which God blesses. For has He not said, "The eyes of the Lord run to and fro throughout the whole earth to show Himself strong in behalf of them whose heart is perfect toward Him"? At this point none need fail, and yet, what an awful thing! -- some will fail, and after having, as they say, prophesied in His name, and in His name cast out devils, and in His name done many wondrous works, shall hear Him profess, "I never knew you; depart from Me, ye that work iniquity." "Let nothing now my heart divide, Since with Thee I am crucified, And live to God in Thee. Dead to the world and all its toys, Its idle pomps and fading joys. Jesus, my glory be."