Imaam Ibn Rajab (rahimahullaah) said:
Strive to actualize Tawheed, for indeed (you) cannot reach (the pleasure of Allaah, His Reward and safety from the fire) except by way of it. And be eager to fulfil the rights of Allaah, for indeed you cannot be safe from Allaah’s punishment except by way of fulfilling His Rights.
[Kalimah Al-Ikhlaas. Page 54]