“Do not say, "when I have leisure I will study," for you may never have leisure.”

“According to Cato the Elder, Scipio Africanus was wont to say that he was never less at leisure than when at leisure, nor less alone than when alone.”
P. Scipionem [...] dicere solitum scripsit Cato [...] numquam se minus otiosum esse, quam cum otiosus; nec minus solum, quam cum solus esset.

“Reading is my favourite occupation, when I have leisure for it and books to read.”

“ A good servant should never have any leisure.”

“Everybody was saying we must have more leisure. Now they are complaining they are unemployed.”

“Leisure is the mother of Philosophy; and Common-wealth, the mother of Peace, and Leisure: Where first were great and flourishing Cities, there was first the study of Philosophy.”

“As to that leisure evening of life, I must say that I do not want it. I can conceive of no contentment of which toil is not to be the immediate parent.”

“It is long since I have known the sweets of leisure and repose; since I have known in fine, that indolent but agreeable condition of doing nothing, and being nothing.”
Olim nescio quid sit otium quid quies, quid denique illud iners quidem, iucundum tamen nihil agere nihil esse.

“I made this [letter] very long, because I did not have the leisure to make it shorter.”

“Do not say "When I free myself of my concerns, I will study," for perhaps you will never free yourself.Do not say: "When I am free, I will study"; perhaps you will never be free.”