IQRA Islamic Magazine : "Islam counts envy amongst some of the worst of sins and it stems primarily from disbelief. If we allow the disease of envy to manifest within our hearts, our mind and body get affected too and we are propelled to react wrongly in our actions. We corrode spiritually and move further and further from acting fairly and righteously."
The article Keeping envy at Bay explains the importance of knowing and accepting that there is always wisdom in the Almighty's decision because He knows us like no one else does! If somebody is childless, not wealthy or not beautiful it is for the best of interest of the individual. To see how, read the article.