מוסר אויף תהילים 100:2

The Yalkut on Bereshit (22,9) וישם אותו על המזבח describes both Abraham looking at Isaac, and Isaac looking towards Heaven. Both were crying. The Yalkut presents a most moving picture of the great quantity of tears which covered Abraham from head to toe. All this in order to implore G–d to save Isaac. Abraham told his son that seeing he had wept so many tears, G–d has provided a different offering in his place. At that moment Isaac broke out in bitter cries proclaiming: "I raise my eyes towards the mountains, whence will my salvation come?" (Psalms 121,1). All this proves that both Abraham and Isaac had been willing to go through with the sacrifice, but how could they have been described as having served the Lord with joy, as is required?!

JOY: The second [branch of love of G-d] is joy, it is a great, essential principal in serving G-d. This is what David exhorted us saying: "Serve G-d with joy, come before Him with song" (Tehilim 100:2), and "the righteous will rejoice, they will exult before God and delight with joy" (Tehilim 68:4). And our sages said: "the Divine presence rests on a person only through his rejoicing in a mitzva" (Shabbat 30b). On the aforementioned verse: "Serve G-d with joy", our sages said in a Midrash (Shocher Tov, Tehilim 100): "Rabbi Abahu says: 'when you stand to pray, your heart should rejoice, for you are praying to the Almighty of whom there is none like Him'".

There are two diametrically opposed verses, each one of which purports to tell us how to serve the Lord by prayer. In Psalms 100,2 we are told: עבדו את ה' בשמחה, "Serve the Lord in joy," whereas in Psalms 2,11 we are told: עבדו את ה' ביראה, "Serve the Lord in trepidation, reverence!" The plain meaning of the verses in question is that they apply to prayer which is called עבודה שבלב, "service with the heart." Our sages have said that while praying, we must direct our heart toward Heaven and our eyes towards Earth: Our downcast eyes to remind us of our puniness, our insignificance before G–d the Exalted. Our uplifted heart will induce fear and trepidation so that we may serve the Lord out of true reverence. Once we have attained this level of reverence our heart will contemplate what is above us and thus will be full of joy that we have been found fit to serve such a Master. We note that both emotions are an integral part of prayer.