1 Sam 2:35, “And I will raise me up a faithful priest, that shall do according to that which is in mine heart, and in my mind…”.
Eli and his sons had made a mockery of the priest’s office. So, the Lord said what he was going to do in 1 Sam 2:35. The priest that he raised up is Samuel.
For Samuel to be able to do according to that which was in the heart and mind of the Lord, he would have to know the heart and mind of the Lord. Thus, it appears that the condition of your heart and mind are more important to the Lord than the amount of “head” knowledge you have.
Consider King David. Though he was a sinner and did some awful things, yet, he was a man after God’s own heart, 1 Sam 13:14. And we regard him as on of the best kings Israel ever had. Jesus will sit upon his throne. We are sinners, as well. Yet, we are in the body of Christ as functional members of his body. We must do according to that which is in his heart and mind as revealed to us in the word of God.
When you read the Bible, you should seek to know his mind and heart. We have an advantage as Christians because we have the mind of Christ, 1 Cor 2:16. However, we have to let this mind be in us which was in Christ Jesus, Phil 2:5.
Read the Bible with the desire to know God and to do according to all that is in his heart and mind. This will conform you to the image of Christ, Rom 8:29. His work in us is an inside job.
Samuel “did” according to all that was in the heart and mind of the Lord. According to Jn 14:15, 21, 23, the person who has a heart that loves the Lord will obey God and do what he said. As a result, you won’t turn out like Eli and his sons. You’ll turn out like Samuel.