Appears 4 times in the Quran. (Root: دعو)
  1. There did Zakariya pray to his Lord; he said: My Lord! grant me from Thee good offspring; surely Thou art the Hearer of prayer.

  2. And when distress afflicts a man he calls upon his Lord turning to Him frequently; then when He makes him possess a favor from Him, he forgets that for which he called upon Him before, and sets up rivals to Allah that he may cause (men) to stray off from His path. Say: Enjoy yourself in your ungratefulness a little, surely you are of the inmates of the fire.

  3. Then he called upon his Lord: These are a guilty people.

  4. Therefore he called upon his Lord: I am overcome, come Thou then to help.