And God said, "Let there be light,"and there was light. (Gen 1:3) And God said, "Let there be ..." (Gen 1:6a, 14a) And God said, "Let the ..." (Gen 1:9a, 11a, 20a, 24a) And God said, "Let Us make man ..." (Gen 1:26a)
The Word of God is incredibly powerful. Genesis 1 describes how the entire universe and everything in it was created by the spoken words of God. This is the ultimate definition of the word "efficacy" (and "efficacious", its adjective form), which Merriam-Webster defines as "the power to produce an effect". The spoken Word of God had the power to create the entire universe out of nothing. Talk about producing an effect, creating everything out of nothing!
For the word of God is alive and active. Sharper than any double-edged sword, it penetrates even to dividing soul and spirit, joints and marrow; it judges the thoughts and attitudes of the heart. (Hebrews 4:12)
We might describe the writing of a good author as exciting and page-turning; we might even go so far as to say he makes the story he has written "come alive". However, that is a pale comparison to the description of the Word of God in Hebrews. The Word of God doesn’t simply make the scriptures "come alive" (which it does). The Word of God is itself "alive and active" and able to penetrate the soul of the listener/hearer. While other writings might be "inspirational", none of them can penetrate our souls, can judge our thoughts and our attitudes, can bring us to our knees in repentance. Only the efficacious Word of God can have this effect.
While the words spoken by God can do miraculous things, like creating the universe, the written Word of God (or the written Word of God spoken by one of us) is also powerful, is also capable of miraculous things. The power of God’s Word, even when simply read or spoken by flawed humans, is still efficacious, is still capable of penetrating the souls of the readers/listeners and producing the desired effect of converting their hearts.
so is my word that goes out from my mouth: It will not return to me empty, but will accomplish what I desire and achieve the purpose for which I sent it. (Isaiah 55:11)
The passage above from Isaiah is pretty much the Biblical definition of "efficacy". God’s Word does not come back to Him empty-handed. It accomplishes whatever God desires. It achieves the purpose for which God sent it. This is what "Biblical efficacy" is, the "power of the Word of God to produce the effect that God desires".
So what does this mean for you and me? In the Great Commission (Matthew 28:19-20) God commanded us to teach all nations, to baptize them in the name of the Father, Son and Holy Spirit. So how do we do this? Perhaps even more importantly, how do we do this efficaciously? How do we reach others in such a way that their hearts/souls might be stirred to life? All of us know people that aren’t saved, that don’t believe and trust in Jesus as their Lord and Savior. How do we reach these people? What can we say or do that might convert them?
While we are all expected to be able to give a defense (an apology) of what we believe, using logical reasoning (apologetics) to defend our faith is unlikely to lead others to saving faith (although it can help overcome their barriers to openly listening). For them to be converted we need to share the efficacious Word of God and trust in God that His Word will accomplish what He desires. We can do no more. Our arguments will not change them. The exercising of our will to convert them will not work. Nothing we do by the force of our personality can stir their spirit. Only the efficacious Word of God can accomplish this. Therefore, for our evangelism to be effective, we must (simply) share the Word of God and trust in His Word to do what He desires.
A good example of this was the most recent Christmas Eve service. This service typically has the most visitors and infrequently attending members of any service during the year. In the latest Christmas Eve service, Pastor Waffel read nine passages from the Bible starting with the fall into sin, going through the Messianic prophecies and the birth of Jesus and ending with the beautiful words of John 1. This is a good example of sharing God’s Word and trusting in its efficacy. Regardless of whether anyone’s souls were stirred that night, whether anyone was awakened spiritually, Pastor Waffel did exactly what he should have. He shared the Word of God and trusted that it would accomplish that for which God intended.
We should do the same. Next time the opportunity arises to share your faith, quote some passages from the Bible, preferably some that include Law and, for sure, several that include the wonderful Gospel that Jesus died for our sins!