SB 10.71.8

nimittaṁ param īśasya
hiraṇyagarbhaḥ śarvaś ca
 kālasyārūpiṇas tava
nimittam — the instrument; param — merely; īśasya — of the Supreme Lord; viśva — of the universe; sarga — in the creation; nirodhayoḥ — and the annihilation; hiraṇyagarbhaḥ — Lord Brahmā; śarvaḥ — Lord Śiva; ca — and; kālasya — of time; arūpiṇaḥ — formless; tava — Your.
Even Lord Brahmā and Lord Śiva act only as Your instruments in cosmic creation and annihilation, which are ultimately done by You, the Supreme Lord, in Your invisible aspect of time.

Uddhava here explains that in fact Lord Kṛṣṇa Himself will cause the death of Jarāsandha, and Bhīma will merely be the instrument. The Supreme Lord, through His invisible potency of time, creates and annihilates the entire cosmic situation, whereas great demigods such as Lord Brahmā and Lord Śiva are merely the instruments of the Lord’s will. Therefore Bhīma will have no difficulty acting as the Lord’s instrument to kill the powerful Jarāsandha. In this way, by the Lord’s arrangement, His devotee Bhīma will be glorified.