Imagine a wife saying: “99.9% of my heart belongs to my husband. The 0.1% is still with another man, but the rest (an overwhelming majority) is for my husband.”
99.9% is indeed the vast majority—and yet no husband in the world would be satisfied with that. Only when he has the whole heart, i.e., 100%, he would be happy.
The Lord also has this claim concerning our hearts. As the above example shows, this is easy to understand. Scripture says that we should have an “undivided devotion to the Lord” or “serve without distraction” (1 Corinthians 7:35), i.e., with our whole heart. This is why the Lord Jesus Himself says: “You shall love the Lord your God with all your heart, with all your soul, and with all your mind” (Matthew 22:37). It is also interesting to note that the prophets of the Old Testament often apply unfaithfulness in a relationship to God and the faithful (Jeremiah 2:2; Hosea 2:4, 15, 18, 21, 22).
For this reason, the Book of Exodus also speaks of a “jealous God” (Exodus 20:5) when he calls on the people to serve the Lord completely and not the gods. This does not mean that God is as jealous as we humans often are; rather, it shows that He cannot allow anything to compete with Him for our hearts. He is justified to claim 100%.
Probably every Christian would like to say that 100% of his heart belongs to the Lord. Our practice (specifically: our use of time, energy, and money, as well as our living out our relationship with the Lord) shows whether this is indeed the case.
The Lord always gave and gives us 100%—we want to love Him back in the same way!