Kamasutra 5.6.46

5.6.46

saṃdṛśya śāstrato yogān pāradārikalakṣitān/
na yāti cchalanāṃ kaścit svadārān prati śāstravit//

"A clever man, learning from the Shastras the ways of winning over the wives of other people, is never deceived in the case of his own wives. No one, however, should make use of these ways for seducing the wives of others, because they do not always succeed, and, moreover, often cause disasters, and the destruction of Dharma and Artha. This book, which is intended for the good of the people, and to teach them the ways of guarding their own wives, should not be made use of merely for gaining over the wives of others."