If you don't have access to a gym or other fitness equipment and your goal is to increase your strength, look at the Recommended Routine on Reddit. This routine of bodyweight exercises, carried out consistently over time, will hugely improve the strength of an untrained individual. As a consequence, you will also add muscle and lose fat. The overall effect on body mass will likely be neutral, but body composition should improve.
In order to add significant (>5%) body mass as a result of any resistance exercise routine, you need to undertake it for a significant period while also maintaining a significant ongoing calorie surplus. To get big, you need to eat big. If your diet is sufficient for your activity (but not in surplus), you won't increase in size.