Camus, The Plague, Penguin Modern Classics, 1967, p236:

"Then they had resumed their silent vigil. From time to time Mme Rieux stole a glance at her son and, whenver he caught her doing this, he smiled... then once more the quiet breathing of the night.
'Bernard?'
'Yes?'
'Not too tired?'
'No.'
At that moment he knew what his mother was thinking, and that she loved him. But he knew, too, that to love someone means relatively little; or, rather, that love is never strong enough to find the words befitting it. Thus he and his mother would always love each other silently"..

Happy Birthday Mum....