Psalm 125:2 uses the geographical feature of Jerusalem being surrounded by mountains as a metaphor for the protective presence of God (Yahweh) around His people. Let's break down the meaning:

"As the mountains surround Jerusalem...": Jerusalem is situated in a mountainous region. The mountains provide a natural defense and a sense of stability. They were a physical barrier against enemies and a constant, unchanging presence.

"...so Yahweh surrounds his people...": This draws a direct comparison. Just as the mountains encircle Jerusalem, Yahweh (God) figuratively encircles His people. This implies protection, security, and an unwavering presence.

"...from this time forward and forever more.": This emphasizes the permanence of God's protection. It's not just a temporary shield but a continuous, never-ending promise.

In essence, the verse means:

God's Protection: God provides a protective presence for His people, much like the mountains protect Jerusalem.
God's Security: God's presence offers security and stability. They are safe and secure because of God.
God's Constant Presence: God's protection is not temporary; it is a permanent and unwavering aspect of His relationship with His people. It's an eternal promise of support and defense.

Key Takeaways:

Metaphorical Language: The verse is highly metaphorical, using a tangible image (mountains surrounding a city) to convey an abstract concept (God's protection).
Assurance and Comfort: The verse is intended to provide assurance and comfort to God's people, reminding them of His ever-present protection.
Relationship: It speaks to the relationship between God and His people, highlighting His role as their protector and provider.

The verse is a powerful affirmation of God's unwavering commitment to care for and defend those who trust in Him. It's a reminder that even in the face of challenges, God's people are surrounded by His loving and protective presence, now and forever.