Legolas has killed thirty-nine orcs

A broad stairway climbed from the Deep up to the Rock and the rear-gate of the Hornburg. Near the bottom stood Aragorn. In his hand still Andúril gleamed, and the terror of the sword for a while held back the enemy, as one by one all who could gain the stair passed up towards the gate. Behind on the upper steps knelt Legolas. His bow was bent, but one gleaned arrow was all that he had left, and he peered out now, ready to shoot the first Orc that should dare to approach the stair.

‘All who can have now got safe within, Aragorn,’ he called. ‘Come back!’

Aragorn turned and sped up the stair; but as he ran he stumbled in his weariness. At once his enemies leapt forward. Up came the Orcs, yelling, with their long arms stretched out to seize him. The foremost fell with Legolas’ last arrow in his throat, but the rest sprang over him. Then a great boulder, cast from the outer wall above, crashed down upon the stair, and hurled them back into the Deep. Aragorn gained the door, and swiftly it clanged to behind him.

‘Things go ill, my friends,’ he said, wiping the sweat from his brow with his arm.

‘Ill enough,’ said Legolas, ‘but not yet hopeless, while we have you with us. Where is Gimli?’

‘I do not know,’ said Aragorn. ‘I last saw him fighting on the ground behind the wall, but the enemy swept us apart.’

‘Alas! That is evil news,’ said Legolas.

‘He is stout and strong,’ said Aragorn. ‘Let us hope that he will escape back to the caves. There he would be safe for a while. Safer than we. Such a refuge would be to the liking of a dwarf.’

‘That must be my hope,’ said Legolas. ‘But I wish that he had come this way. I desired to tell Master Gimli that my tale is now thirty-nine.’

‘If he wins back to the caves, he will pass your count again,’ laughed Aragorn. ‘Never did I see an axe so wielded.’

‘I must go and seek some arrows,’ said Legolas. ‘Would that this night would end, and I could have better light for shooting.’

The Two Towers, Book Three, Chapter 7: Helm's Deep.