Reference: Siyar A’laam an-Nubalaa – Volume 4, Page 321
Sa’eed ibn Jubayr said:
at-Tawakkul (complete trust and reliance) upon Allaah [alone] is the culmination of [one’s] eemaan.
And he would supplicate [to Allaah, saying]:
الَّلهُمَّ إِنِّي أَسْأَلُكَ صِدْقَ التَّوَكُّلِ عَلَيْكَ وَ حُسْنَ الظَّنِّ بِكَ
O Allaah, indeed I ask You [to bless me with] genuine tawakkul (complete trust and reliance) upon You, and [to always] have good suspicion of You.