It is deemed best practice to always use
Option Explicit in VBA as it forces the developer to declare all their variables before use. This has other benefits too, such as auto-capitalization for declared variable names and IntelliSense.
Option Explicit Sub OptionExplicit() Dim a As Integer a = 5 b = 10 '// Causes compile error as 'b' is not declared End Sub
Setting Require Variable Declaration within the VBE's Tools ► Options ► Editor property page will put the Option Explicit statement at the top of each newly created code sheet.
This will avoid silly coding mistakes like misspellings as well as influencing you to use the correct variable type in the variable declaration. (Some more examples are given at ALWAYS Use "Option Explicit".)