Objection 1. It would seem that the temptation of God is not opposed to the virtue of religion. The temptation of God is sinful, because a man doubts God, as stated above (Article 2). Now doubt about God comes under the head of unbelief, which is opposed to faith. Therefore temptation of God is opposed to faith rather than to religion.
Objection 2. Further, it is written (Sirach 18:23): "Before prayer prepare thy soul, and be not as a man that tempteth God. Such a man," that is, who tempts God, says the interlinear gloss, "prays for what God taught him to pray for, yet does not what God has commanded him to do." Now this pertains to imprudence which is opposed to hope. Therefore it seems that temptation of God is a sin opposed to hope.
Objection 3. Further, a gloss on Psalm 77:18, "And they tempted God in their hearts," says that "to tempt God is to pray to Him deceitfully, with simplicity in our words and wickedness in our hearts." Now deceit is opposed to the virtue of truth. Therefore temptation of God is opposed, not to religion, but to truth.
On the contrary, According to the gloss quoted above "to tempt God is to pray to Him inordinately." Now to pray to God becomingly is an act of religion as stated above (Question 83, Article 15). Therefore to tempt God is a sin opposed to religion.
I answer that, As clearly shown above (Question 81, Article 5), the end of religion is to pay reverence to God. Wherefore whatever pertains directly to irreverence for God is opposed to religion. Now it is evident that to tempt a person pertains to irreverence for him: since no one presumes to tempt one of whose excellence he is sure. Hence it is manifest that to tempt God is a sin opposed to religion.
Reply to Objection 1. As stated above (Question 81, Article 07), it belongs to religion to declare one's faith by certain signs indicative of reverence towards God. Consequently it belongs to irreligion that, through doubtful faith, a man does things indicative of irreverence towards God. To tempt God is one of these; wherefore it is a species of irreligion.
Reply to Objection 2. He that prepares not his soul before prayer by forgiving those against whom he has anything, or in some other way disposing himself to devotion, does not do what he can to be heard by God, wherefore he tempts God implicitly as it were. And though this implicit temptation would seem to arise from presumption or indiscretion, yet the very fact that a man behaves presumptuously and without due care in matters relating to God implies irreverence towards Him. For it is written (1 Peter 5:6): "Be you humbled... under the mighty hand of God," and (2 Timothy 2:15): "Carefully study to present thyself approved unto God." Therefore also this kind of temptation is a species of irreligion.
Reply to Objection 3. A man is said to pray deceitfully, not in relation to God, Who knows the secrets of the heart, but in relation to man. Wherefore deceit is accidental to the temptation of God, and consequently it does not follow that to tempt God is directly opposed to the truth.
Source: Summa Theologica (New Advent)