what happens if a spider bites your clothes will its venom be on it?

nothing

No.

It is possible that a spider that bites your clothes will leave behind some venom, but venom has to get past your skin to have any effect on your clinically. That means if you have no cuts on your skin, touching the venom won't harm you. Venoms are usually not corrosive, meaning they won't damage you skin and then get inside your body, Many venoms will also dry out when exposed to air, making them even less dangerous.

It is possible a spider could leave some venom biting clothing, but something to consider here, venom is not a poison, so it would just be totally harmless. What makes venom toxic is being injected into the skin.
It is not toxic to touch, or even eat for that matter.
There are so few spiders that are even toxic to humans with a bite, that in itself makes them harmless.
If you ever wonder why such a small critter like an ant sting can hurt as bad as it does, it is the venom produced by an ant, much the same for a bee. Still regarded as harmless.

It will bite and the venom will be injected into the clothing, but as long as you have not an open cut for it to get into your blood stream then it wont affect you