Translation:

16. (And Allah's Message is): "If they (the pagans) had (only) remained on the (right) Way We should certainly have bestowed on them Rain in abundance.

Notes (Tafseer)

5740. Rain: literally, water: stands for all kinds of blessings, material, moral, and spiritual. All blessings come by way of trial: the more we have, the more is expected of us. A man of gifts, talents, or insight is expected to show a higher standard of love and unselfishness than one less gifted, just as a rich man is expected to give more in charity than a poor man.