...he who touches the earth and it melts...? Who was Prophet Amos referring to in the statement above?

This statement comes from Amos 9:5, which reads: "The Lord GOD of hosts, he who touches the earth and it melts, and all who dwell in it mourn." Prophet Amos was referring to the Lord, God of hosts (Yahweh, the God of armies).

The title "Lord, God of hosts" (or "Lord God Almighty") is a specific Old Testament designation that emphasises God's supreme authority over all powers, both heavenly and earthly. The imagery of touching the earth and causing it to melt conveys God's absolute power over creation - even the solid earth dissolves at His touch.

Amos used this description as part of a doxology (hymn of praise) to remind Israel of God's overwhelming majesty and power. The purpose was to warn the Israelites that the God who could melt the earth was the same God they had offended with their social injustice and religious hypocrisy. This is a direct title for God Himself, not a reference to angels, heavenly hosts as separate beings, or a "saviour" figure distinct from God.