Since others have posted the full quote, I'll post Samir Amin's interpretation of it:

Nevertheless, another reading can be made of Marx. The often cited phrase--"religion is the opium of the people"--is truncated. What follows this remark lets it be understood that human beings need opium, because they are metaphysical animals who cannot avoid asking themselves questions about the meaning of life. They give what answers they can, either adopting those offered by religion or inventing new ones, or else they avoid worrying about them.

In any case, religions are part of the picture of reality and even constitute an important dimension of it. It is, therefore, important to analyze their social function, and in our modern world their articulation with what currendy constitutes modernity: capitalism, democracy, and secularism... It will be seen that the [Abrahamic] religions in question have been subject to successive interpretations, which have enabled them to survive, adapt to gigantic social transformations, and even participate in those transformations.