When someone believes that Jesus existed as a man on earth, but they don’t believe that He was the Son of God, who became a man to voluntarily die on the cross, thereby paying the price for all of our sins, it is not real saving belief. Jesus was the Creator, and only the Creator could become a man, live a sinless life, and take upon Himself the sins of the world. If your friend believes that Jesus existed, but that He didn’t do everything that the Bible says, his/her belief is useless, and it will not save anyone. Remember, even the demons believe that Jesus existed as a man, and even believe that He was also God, but that doesn’t save them.

James 2:19   You believe that there is one God. You do well. Even the demons believe—and tremble!

John 1      ¹ In the beginning was the Word, and the Word was with God, and the Word was God. ² He was in the beginning with God. ³All things were made through Him, and without Him nothing was made that was made.

¹⁴ And the Word became flesh and dwelt among us, and we beheld His glory, the glory as of the only begotten of the Father, full of grace and truth.

Colossians 1   ¹³ He has delivered us from the power of darkness and conveyed us into the kingdom of the Son of His love, ¹⁴ in whom we have redemption through His blood, the forgiveness of sins. ¹⁵ He is the image of the invisible God, the firstborn over all creation. ¹⁶ For by Him all things were created that are in heaven and that are on earth, visible and invisible, whether thrones or dominions or principalities or powers. All things were created through Him and for Him. ¹⁷ And He is before all things, and in Him all things consist. 

Hebrews 1      God, who at various times and in various ways spoke in time past to the fathers by the prophets, ² has in these last days spoken to us by His Son, whom He has appointed heir of all things, through whom also He made the worlds;

The Bible is the Word of God, written by about 40 different people, all inspired by God. But if we do not believe that the Bible is completely true, divine, capable of changing our lives totally, then it helps us not a bit. Your friend has a mental belief, but if he/she does not get to know the God of the Bible, the Saviour of the Bible, and believes that Jesus paid the price for her/his sins, then God cannot help. God gives every one of us the power of free choice, and He honours our choices, and never interferes, so the outcome is determined by your friend’s choice. All you can do is live a life that reflects God, so that your words and actions are in harmony, which will help to draw your friend to Jesus. And never stop praying that your friend will make the right choice, to believe everything the Bible says about Jesus.

2 Peter 1     ²⁰ … no prophecy of Scripture is of any private interpretation, ²¹ for prophecy never came by the will of man, but holy men of God spoke as they were moved by the Holy Spirit.

2 Timothy 3:16   All Scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness …

1 Peter 1:25   the word of the Lord endures forever.

Matthew 24:35   “Heaven and earth will pass away, but My words will by no means pass away.”

I trust that this makes sense to you. God bless!