"If government wishes to tax certain goods, it should tax goods that have inelastic rather than elastic demand." What is the rationale for this statement?

The rationale for this statement is fairly straightforward. "Elasticity" of demand refers to the extent to which demand will change along with price. For example, gasoline is fairly demand inelastic, because people and business need it. So the demand for gasoline will probably stay roughly the same even if its price goes up. Demand for some other goods that are not necessities, like designer clothing or electronics, will be affected by price increases. People will demand less of them if their price is too high.
Anytime a government taxes a good, the tax is passed on to the consumer in the form of price increases. In order for the tax to raise revenue, people have to keep purchasing the good. Therefore it could be self-defeating to place a tax on an item with a very elastic demand. People will just stop buying it. So it makes sense (at least fiscal sense) for governments to tax items that people have to buy. On the other hand, if a government is seen as responsible for significant price increases on necessary items, they may pay a political cost.
https://www.investopedia.com/terms/e/inelastic.asp

Goods that have inelastic demand are goods that consumers buy at the same rate whether the price is high or low. These goods tend to be items people need no matter what the cost—for example, gasoline or medical services. Demand varies depending on the price of items with elastic demand. These items typically have other competitors who pick up their buyers if their price goes too high. For example, soda could be considered an elastic demand good. If the price of soda skyrockets, consumers will purchase other beverage options such as water, juices, coffees, and so on.
Taxing a product will increase its cost. If you tax a product with inelastic demand, that product will continue to be bought at the same rate. However, if you tax an elastic demand product, the rise in cost will result in consumers moving their purchase to a different product. A reduction in sales will result in less tax revenue generated. To ensure maximum tax revenue, therefore, the government should tax inelastic demand items.