Adam Clarke on 2 Samuel 2:7

Now let your hands be strengthened - David certainly wished to attach the men of Jabesh to his interest; he saw that they were generous and valiant, and must be of great service to him whose part they espoused; and he was no doubt afraid that they would attach themselves to the house of Saul, in consideration of the eminent services Saul had rendered them in rescuing them from Nahash, king of the Ammonites.