When such love is wanting, we cannot do the will of our Lord unceasingly, for He does not reward us with worldly honors and wealth, but with life everlasting. This is what Christ teaches us here. He tells us: My reward you will obtain in the life to come; therefore you must above all things have love towards me, for then you will adhere to my Word under all circumstances, even at the risk of your life. But if this love is lacking in your hearts you will not keep my Word, but will yield to danger, adversity and tribulation, which will finally plunge you into impatience and despair.

He who knows Christ in true faith and love will not be dismayed at these adversities, but will meet them boldly, convinced of the assistance of his Lord, and strong in the knowledge that He died, was buried, and arose again for us, and that therefore He cannot be opposed to our welfare. Thus love is intimately connected with faith and overcomes all danger and misfortune, without regarding the displeasure and wrath of the world. True love concerns itself about Christ and His Word, and pays no attention to the anger of the world. (Luther’s House Postil, Second Sermon for Pentecost, Volume 2, p. 599-600)

The word “love” is also used in this connection, because Christ foresaw with what great difficulties he would have to contend who would receive His Word and persevere in it. Manifold tribulations, which tend to arouse impatience and dissatisfaction, will present themselves. Besides these, the temptation is near at hand to think: I am myself to blame for what I endure; why did I preach and confess the Word publicly? If I had kept my peace and had exercised within myself only the faith in God’s Word and His gifts, no one would have molested me, and others, more competent than I, might have more successfully undertaken the task of a public confession and of teaching. Now I am in a great strait, for I am not only unsuccessful in my attempt, but am also in danger of losing my life for it. Such disquieting thoughts and temptations to despair cannot be overcome and banished from our hearts, nor can we immovably adhere to the Word, unless we have within us that love, of which Christ speaks in our text. Then every preacher, yea, every Christian, can exclaim: Let happen what will, I will nevertheless hold fast to the Word and will never deny my Lord and Saviour; for I enlisted in His cause for His glory, and not to please men, therefore I will endure all to the very end. (Luther’s House Postil, Second Sermon for Pentecost, Volume 2, p. 599)

This Gospel (John 14:23-31) is a part of the exhortation which Christ addressed to His disciples on the evening before His sufferings, and contains words of especial importance. Christ would teach us in these words how vain is the endeavor to obtain a knowledge of God and to come to Him without loving: the Saviour. Where this is wanting, our thoughts of God and our devotion are without assurance and we cannot apprehend Him. But if we love Christ we can come to the Father and He will love us.  How is it that Christ here speaks of love and does not say, as He is wont to say: “Believe in me?” Is love more efficacious than faith that He says: “If a man loves me?” We answer: The sense is the same; man cannot truly love Christ unless he believes in Him and is comforted in Him. The word “love” is in this case plainer and more forcible, because it indicates so nicely, how our hearts should turn from everything else in heaven and on earth, and should cling alone to this Man, Jesus Christ. For we know how love, according to its
very nature, concentrates all its energies upon the object of its devotion, and remains attached to it, regardless of aught else in the wide world. It is the Lord’s will that we should thus cherish and love Him with our whole heart. This we cannot do except through faith. Hence this declaration concerning love does not in the least detract anything from faith, but rather instructs us as to the true character and efficacy of faith. (Luther’s House Postil, Second Sermon for Pentecost, Volume 2, p. 598-599)