Delete row if column contains string

I cannot get the following code to do what I want

Sub VerwijderNtRelevant()
    Dim waarde As String
    Dim teller As Long
    
    teller = 4
    
    For teller = 4 To 517 Step 1
        waarde = Cells(teller, 13).Value
        If InStr(1, waarde, "ADH", vbTextCompare) = 0 Then
            Cells(teller).EntireRow.Delete
        End If
    Next teller
End Sub

I want to go through rows 4 to 517 and see if column M (= column 13) contains the string 'ADH'. If it does, nothing should happen. If it does not, the row should be entirely deleted.
The value in column M could be something like 'BBR, ADH, HE' or 'KFE' or 'BH, HE'.

Any help will be greatly appreciated.