I’ve seen this thought elsewhere, but I wonder if this is the first instance of its appearing.
Let us therefore abide in the things which we believed, in righteousness and holiness, that we may with boldness ask of God who saith, Whiles thou art still speaking I will say, Behold I am here. For this word is the token of a great promise: for the Lord saith of Himself that He is more ready to give than he that asketh to ask.
An Ancient Homily by an Unknown Author (otherwise known as 2nd Clement), 15 (from Lightfoot’s Apostolic Fathers)