Whoever therefore sees (with insight)...
Whoever therefore sees (with insight), it is to his own gain, and whoever be blind, it is to his own loss; and am not a keeper over you." "Certainly clear proofs have come to you from your Lord....." The term /basa'ir/ is the plural form of /basirat/ which means some indications and guidance by which the truth will be manifested. It also means the light of the heart (mind), while /basar/ means the light of the eye.
Then the phrase means that they have come to you from your Lord with the purpose of paying attention to this matter that what is right to Allah and what is not. By means of the divine revelation, there have come down some information that are considered as a light and the power of sight for your hearts (minds). "...
Whoever therefore sees (with insight), it is to his own gain, and whoever be blind, it is to his own loss; That is, the person who looks at the Truth and believes in it, has worked for his own profit; and the one who relinquishes it, has acted toward his own loss. It is understood from this verse that people are not obliged in doing their affairs. They are free and authorized in choosing them and performing them.
"And thus do We repeat the Signs, that they may say (unto you): "You have studied" and that We may make it clear to a people who know." In order to emphasize that the final decision for choosing the way of right and the way of wrong is upon the servants of Allah themselves, the verse says: "And thus do We repeat the Signs...." But a group of the opponents may oppose you and, without having any authentic evidence or research, they say that you have learnt these lessons from the Jews and the Christians, which have been taken from their revealed Books.