Many scriptures relating to adoption/orphans can be found in the Bible. Moses was basically adopted, and Jesus himself was raised with the help of Joseph. Most of all, as a believer, we are adopted into God's Kingdom.
Later, when the boy was older, his mother brought him back to Pharaoh's daughter, who adopted him as her own son. The princess named him Moses, for she explained, "I lifted him out of the water."
Another really good example is Queen Esther who was adopted by her cousin Mordecai:
"He had brought up Hadassah, that is Esther, the daughter of his uncle,
for she had neither father nor mother; the maiden was beautiful and
lovely, and when her father and her mother died, Mordecai adopted her as
his own daughter."
And anyone who welcomes a little child like this on my behalf is welcoming me.
Father to the fatherless, defender of widows — this is God, whose dwelling is holy. God places the lonely in families.
In you the orphan finds mercy.
Never take advantage of any widow or orphan. If you do and they cry out to me, you can be sure that I will hear their cry.
For as many as are led by the Spirit of God, these are sons of God. For you did not receive the spirit of bondage again to fear, but you received the Spirit of adoption by whom we cry out, "Abba, Father."
But when the fullness of the time had come, God sent forth His Son, born of a woman, born under the law, to redeem those who were under the law, that we might receive the adoption as sons.
You are the helper of the fatherless. LORD, You have heard the desire of the humble; You will prepare their heart; You will cause Your ear to hear, To do justice to the fatherless and the oppressed, That the man of the earth may oppress no more.
Pure and genuine religion in the sight of God the Father means caring for orphans and widows in their distress and refusing to let the world corrupt you.
When you are harvesting your crops and forget to bring in a bundle of grain from your field, don’t go back to get it. Leave it for the foreigners, orphans, and widows. Then the LORD your God will bless you in all you do.
Learn to do good. Seek justice. Help the oppressed. Defend the cause of orphans. Fight for the rights of widows.
Speak up for those who cannot speak for themselves; ensure justice for those being crushed. Yes, speak up for the poor and helpless, and see that they get justice.