Goto Configuration >  AppExpert > Rewrite > Actions in the GUI of the appliance.

Click Add as shown in the following screenshot:

Type the name for the action in the Name field, in the Create Rewrite Action dialog box.

Select DELETE_ALL from the Type list.

Type the expression HTTP.RES.FULL_HEADER in the Expression to choose the target text reference to be deleted field.
Note: If you start typing the expression with HTTP, you can select the options that appear to complete the expression

Select text in the Search Rewrite Action dialog box.

Type ETag: in the Pattern section, as shown in the following screenshot:

Click Create

Goto Configuration >  AppExpert > Rewrite > Policies in the Navigation Pane.

Click Add in the Rewrite Policies window.

Type the policy name in the Name field.

Choose the action that you created in Step 7 from the Action list.

Click Add in the Expression section.

Select the expression HTTP.RES.FULL_HEADER.CONTAINS("Etag:") in the Expression section, as shown in the following screenshot. Click OK.
Note: ETag must be typed in the String field 

Click Create.

Click Close.

Goto Configuration >  Load Balancing > Virtual Server

Edit the Virtual Servers node to which you must bind the rewrite policy.

Select the Policies on the Right side

Click on + sign in the Policies

Select Rewrite in the Choose Policy

Select Response in the Choose Type and click Continue

Select > arrow on Policy Binding

Select the Rewrite Policy that is been created on Step 14 and click Bind