The bruised, bloodied Jesus was being led to the cross and as He was going women in the crowd were mourning and lamenting Him.  (Luke 23:27) 
(NASB) Luke 23:23-31 “But Jesus turning to them said, ‘Daughters of Jerusalem, stop weeping for Me, but weep for yourselves and for your children.
29 ‘For behold, the days are coming when they will say, ‘Blessed are the barren, and the wombs that never bore, and the breasts that never nursed.’
30 ‘Then they will begin TO SAY TO THE MOUNTAINS, ‘FALL ON US,’ AND TO THE HILLS, ‘COVER US.’
31 For if they do these things when the tree is green, what will happen when it is dry?’” 

  Jesus quoted the prophets Hosea and Isaiah…
(Amplified Bible) Hosea 10:8 “The high places also of Aven [once Beth(el), house of God, now (Beth-) aven, house of idolatry], the sin of Israel, shall be destroyed; the thorn and the thistle shall come up on their [idol] altars, and they shall say to the mountains, Cover us!  And to the hills, Fall on us!” 

(Amplified Bible) Isaiah 2:19-21 “Then shall [the stricken, deprived of all in which they had trusted] go into the caves of the rocks and into the holes of the earth from before the terror and dread of the Lord and from before the glory of His majesty, when He arises to shake mightily and terribly the earth.
20In that day men shall cast away to the moles and to the bats their idols of silver and their idols of gold, which they made for themselves to worship.
21To go into the caverns of the rocks and into the clefts of the ragged rocks from before the terror and dread of the Lord and from before the glory of His majesty, when He raises to shake mightily and terribly the earth.” 

  Jesus quoted from these two prophets about the reality of the coming Day of God’s Judgment.  It is still future to us.  Those without faith in Christ Jesus still have time to turn to Him in belief that He did die for sins, that His grace and mercy are still being held out to anyone who asks Jesus to be their Savior.  And those who are followers of Christ have no need to fear that day, for Jesus has dealt with our sins freeing us from God’s wrath. 

(NASB) Revelation 6:14-17 “The sky was split apart like a scroll when it is rolled up, and every mountain and island were moved out of their places.
15 Then the kings of the earth and the great men and the commanders and the rich and the strong and every slave and free man hid themselves in the caves and among the rocks of the mountains;
16 and they said to the mountains and to the rocks, ‘Fall on us and hide us from the presence of Him who sits on the throne, and from the wrath of the Lamb;
17 for the great day of their wrath has come, and who is able to stand?” 

  The reality is…there is a day coming in which the Lord will judge sin!  And that day will be the terrible Day of Judgment.  The love of God for us gives us warning!