Genesis 15:8

He said, “O Lord God, how may I know that I will possess it?”

Zacharias said to the angel, “How will I know this for certain? For I am an old man and my wife is advanced in years.”

Then Gideon said to God, “If You will deliver Israel through me, as You have spoken,

Now Hezekiah said to Isaiah, “What will be the sign that the Lord will heal me, and that I shall go up to the house of the Lord the third day?”

Show me a sign for good,
That those who hate me may see it and be ashamed,
Because You, O Lord, have helped me and comforted me.

“Ask a sign for yourself from the Lord your God; make it deep as Sheol or high as heaven.”

Abraham said to his servant, the oldest of his household, who had charge of all that he owned, “Please place your hand under my thigh,

Behold, I am standing by the spring, and the daughters of the men of the city are coming out to draw water;

So Gideon said to Him, “If now I have found favor in Your sight, then show me a sign that it is You who speak with me.

If they say to us, ‘Wait until we come to you’; then we will stand in our place and not go up to them.

Mary said to the angel, “How can this be, since I am a virgin?”

Treasury of Scripture Knowledge

And he said, Lord GOD, whereby shall I know that I shall inherit it?