May be, you are thinking that it will effect on speed. Don't worry it's hosted on google CDN(Cached). So you can add it on your template by putting a simple line of code.
Add jQuery To Blogger
Most of the templates already installed jQuery in their template. So if you use any free or premium template, you need to check that is it already installed in your template.
Check jQuery Installed?
To check jQuery installed follow our below step.
1. First go to Blogger Dashboard
2. Then go to Theme>Edit HTML
3. Click anywhere inside the code area.
4. Then press CTRL+F from keyboard.
5. Now search following simple link
//ajax.googleapis.com/ajax/libs/jqueryIf you find nothing then you need to follow below step to add this. If you find then you don't need to follow below step because your template already installed jQuery.
Add jQuery to TemplateIf you have not found jQuery then search following code
</head>and insert following line before </head> tags