In Jesus' name, let us come together in prayer and consideration for you, dear seeker.
Firstly, it is commendable that you have brought this matter to God in prayer, as He cares for all aspects of our lives, including our relationships. It is clear that you have deep feelings for your friend and that you desire God's will for this situation. This is a complex matter, and it's important to discern if you are aligned to the teachings of God in this matter.
The Bible tells us to be equally yoked with believers. Do not be unequally yoked with unbelievers. For what fellowship has righteousness with lawlessness? And what communion has light with darkness? (2 Corinthians 6:14 WEB). As you consider this relationship, it's crucial to ensure that you are both believers in Jesus Christ and that you are not being drawn to the world by this relationship.
If you are both Christians that would be wonderful. The closeness of your relationship and the fact you are considering marriage is important. It is our sincere advise you seek marriage to avoid the temptation of sexual immorality. It is not a sin to have a crush on someone but it is a sin to act on the crush in a way that would jeopardize your or the other person's relationship with the Lord.
If the Lord has placed this desire on your heart for marriage, then it is important to bring this to Him in prayer, expressing your feelings honestly and seeking His guidance. In this, God's Word says, Delight yourself also in the Lord, and He will give you the desires of your heart. Commit your way to the Lord. Trust also in Him, and He will do this, (Psalm 37:4-5 WEB). It is important to acknowledge how you feel but also to commit your feelings to God and trust Him with the outcome.
However, it is also crucial to understand that God's will may not align with our desires. If this man is not meant to be your spouse, God may be calling you to surrender these feelings and trust Him with your future. The Bible tells us, For I know the thoughts that I think toward you, says the Lord, thoughts of peace, and not of evil, to give you hope and a future, (Jeremiah 29:11 WEB). Trust that God has a plan for you and and your friend, including your future spouse, whoever that may be.
It is concerning that you mention being willing to remain only a best friend to love and support him. While friendship is a noble and valuable aspect of any relationship, it's important to ensure that you are not settling for less than God's best for you. If you feel called to marriage with this person, pray fervently about this and seek God's face. Do not settle for something less because you are concerned about the future. God will provide if He does indeed intend for you to be together.
Let us pray together:
Dear Heavenly Father,
We come before You today, lifting up our dear seeker who is grappling with their feelings for their friend. Lord, we ask that You give them clarity and discernment as they navigate this situation. Help them to surrender their desires to You and trust in Your plan for their life and their friend, including their future spouse.
If this relationship is not Your will, Father, we ask that You help them to release these feelings and find peace in Your sovereignty. If it is Your will, Father, we ask that You guide them towards a godly marriage that honors You.
In Jesus' name, we pray for strength, wisdom, and courage. Help them not to settle for less than Your best. Give them the grace to walk in purity and integrity, fleeing from any temptation that may come their way.
Lord Jesus Christ, You arrived to save us from our sins. Please be with them and guide them in righteousness. We thank You for Your unfailing love and faithfulness.
In Jesus' name, we pray. Amen.
Prayer Focus: God, Thank You for loving me. God, I ask You in Jesus’ name please bless me with everything that I stand in need of and everything You want me to have. 
