Psalm 24:7 Lift up your heads, you gates; be lifted up, you ancient doors, that the King of glory may come in.
The temple gates were huge and magnificent and probably very hard to open each time a person wanted to come in or out.
They probably had a small secondary gate or door which could be opened up to allow people in and out – but for someone like a king, the whole gate would be opened up fully!
God is saying we are as important as our king, King Jesus, who is stepping forward to invite us in, personally.
God say we should expect the whole gate to open because we are His children.