SB 3.8.12

चतुर्युगानां च सहस्रमप्सु स्वपन्स्वयोदीरितया स्वशक्त्या ।
कालाख्ययासादितकर्मतन्त्रो लोकानपीतान्ददृशे स्वदेहे ॥१२॥

catur-yugānāṁ ca sahasram apsu
svapan svayodīritayā sva-śaktyā
kālākhyayāsādita-karma-tantro
lokān apītān dadṛśe sva-dehe

catuḥ—four; yugānām—of the millenniums; ca—also; sahasram—one thousand; apsu—in the water; svapan—dreaming in sleep; svayā—with His internal potency; udīritayā—for further development; sva-śaktyā—by His own energy; kāla-ākhyayā—by the name kāla; āsādita—being so engaged; karma-tantraḥ—in the matter of fruitive activities; lokān—the total living entities; apītān—bluish; dadṛśe—saw it so; sva-dehe—in His own body.

The Lord lay down for four thousand yuga cycles in His internal potency, and by His external energy He appeared to be sleeping within the water. When the living entities were coming out for further development of their fruitive activities, actuated by the energy called kāla-śakti, He saw His transcendental body as bluish.

In the Viṣṇu Purāṇa, kāla-śakti is mentioned as avidyā. The symptom of the influence of the kāla-śakti is that one has to work in the material world for fruitive results. The fruitive workers are described in Bhagavad-gītā as mūḍhas, or foolish. Such foolish living entities are very enthusiastic to work for some temporary benefit within perpetual bondage. One thinks himself very clever throughout his life if he is able to leave behind him a great asset of wealth for his children, and to achieve this temporary benefit he takes the risk of all sinful activities, without knowledge that such activities will keep him perpetually bound by the shackles of material bondage. Due to this polluted mentality and due to material sins, the aggregate combination of living entities appeared to be bluish. Such an impetus of activity for fruitive result is made possible by the dictation of the external energy of the Lord, kāla.