Ralph Erskine explains below how it is that all things given by God the Father, Son, and Holy Spirit still belong to God:
“The Father loveth the Son, and hath given all things into his hand.” (John 3:35)
[God] is the giver of all things, and the possessor of all things; insomuch that, when he gives all things, he cannot lose thereby the possession of any thing he gives; for, the Father’s giving all things into Christ’s hand doth not imply that he alienates his own right. It is true, when we give a thing to another, we lose a right to it; but it is not so with God; for when he gives all things to Christ, and when he gives Christ, and all things in him to us, he still keeps his right to all that he gives; “All things are yours, and ye are Christ’s, and Christ is God’s,” 1 Cor. 3:22, 23. Thus, what the Father gives into Christ’s hand, remains still in the Father’s hand; “And I give unto them eternal life, and none shall pluck them out of my hand. My Father which gave them me is greater than all, and none is able to pluck them out of my Father’s hand. I and my Father are one,” John 10:28. . . .
This donative (gifting) right that he hath, as Mediator, as it is well adapted to him, who, as God, hath the same essential right and title to all things with the Father and the Holy Ghost. For, as to his eternal Godhead, he is the everlasting Father, Isaiah 9:6, whose goings forth have been of old, from everlasting, Micah 5:2. “By whom are all things, and we by him,” 1 Cor. 8:6. And, as Mediator, his donative right is attended with an acquisitive right, by his purchase, by which he hath merited and obtained a name above every name, and a being head over all things to the church, Phil. 2:97 Eph. 5:23. A bellical [martial] right, by conquest, making the people to fall under him, Psalm 110:4; making them willing in a day of his power, Psalm 110:3; and overcoming those that make war with him, Rev. 17:14. He is able to subdue all things to himself,” Heb. 2:8. An hereditary right, being the heir of all things, Heb. 1:2, and being the first-born, higher than the kings of the earth, Psalm 89:27; the first born from the dead, that in all things he might have the pre-eminence, Col. 1:18. (Heaven’s Grand Repository)