(emphasis mine)
We know that we have come to know him if we keep his commands. Whoever says, “I know him,” but does not do what he commands is a liar, and the truth is not in that person. But if anyone obeys his word, love for GOD is truly MADE COMPLETE IN THEM. This is how we know we are in him: Whoever claims to live in him must live as Jesus did.

When we begin to learn about life and are taught by good parents, obedience is a lesson that we have to learn over and over again. As some examples, good parents teach their kids to: 1) Look both ways before crossing the street, 2) Eat your dinner and vegetables before having dessert, 3) Clean up after yourself, 4) Finish the jobs you start, 5) Work towards excellence in all you do, and 6) Be kind and thoughtful to help those around you.

As we grow up, we realize that obedience is required in many different areas of life. In marriage we sign a covenant to remain faithful to our spouses and God calls us to obey this covenant. As we have children we are called to raise them up in the ways of the Lord, as we work, we are called to work as unto the Lord, etc.

Over time, we get to choose who we listen to, who we will obey. This is a sign of love and devotion to these people, typically. And by obeying these people, we get to know them, to understand their hearts.

John says this is also how we get to know God. We must obey his commands. Some of these commands involve acts of service, others are disciplines we build into our life to connect with God, like prayer, memorization, and Bible study. Some involve the attitudes we are to operate under, others involve the passion and life focus we are to live with.

As we learn of these commands, we have a choice to make: will we follow and obey them? If we say we know God, but do not obey his commands, John says we are liars. This is a severe statement and one we need to pay attention to.

Some in churches these days give lip service to following God, but fail the obedience test of a true follower. Instead, they focus on knowledge only. John here says knowledge of God does not count, if it is not combined with obedience to God. And if we are honest, we know this makes good sense.

To truly get to know the heart of another we must obey them, seek to please them, and understand what moves them. So if we want to be MADE COMPLETE in God, we must obey him. Then his words and actions are in us, and his Spirit has free reign to transform us to be like him.

Lord, I want to be like you. I want to love like you do, bold and big and gentle and humble. I want to care about others like you do. I want to be selfless like you were. Help me to seek your heart and obey your commands each day! Take my heart as yours, dear Lord!