He will come with the clouds.
When he left our planet, he was carried aloft by a cloud (Acts 1:9). The angels told the disciples that he will come in the same way as you saw him go into heaven
(Acts 1:11). This is the promise repeated here. Clouds are God’s vehicle which he rides to his destination (see Psalm 104:3).
7 Behold, he is coming with the clouds, and every eye will see him, even those who pierced him, and all tribes of the earth will wail on account of him. Even so. Amen.