Maybe I'd heard it somewhere already. When you're as old as I am, and been in church since the womb, you hear things but you don't really hear them.
Such is the case with Isaiah 40:31. This was the verse of our cheerleading squad when I cheered for the Harford Christian Eagles in the 1900s. (Back when I was more engine than caboose.)
"They that wait upon the Lord shall renew their strength. They shall mount up with wings as eagles, they shall run and not be weary; they shall walk and not faint."
I think I had heard in more than one sermon what the phrase "wait on God" meant, but what stuck in my head was "wait for God." Endless waiting, it seemed, at times. Waiting for explanations, waiting for healing, waiting for direction, waiting for relationships, waiting for babies, waiting for ...God to do something in the future, and the sooner the future could get here, the less I hated waiting.
But Beth Moore's book study, A Heart Like His, has sealed the meaning in my mind. Thank You, Lord, for Beth Moore. Her style of writing and teaching is so perfectly matched to my way of learning. She explained that "wait on God" means "hope in God."
Hoping is active; waiting is passive. Hoping gives me something to occupy my heart with. It's Godward, not selfward. (Is selfward a word? If it wasn't yet, it is now.) I can hope in God right now whether He grants me my petition or not. I can hope in God because He has never failed me. I can hope in God because He gives me grace to hope in Him.
Hoping in God also sheds proverbial light on this axiom from the OT: Hope deferred makes the heart sick.... I used to think that meant, "If what I hope for seems to never happen, of course I'll be sick about it. My heart will wither to nothing." However, I do believe that I have the power, through the Holy Spirit, to never defer my hope--never put it off till I have more faith or till I see a glimmer of that far-off thing. Rather, I can always hope now. Right now. Hope in God because God is here, God is now, God is faithful, always has been faithful, always will be faithful, so ...what am I waiting for? I'm not! I'm waiting ON God!