Musar for Yevamot 210:11

The incense-offering is the mystical element which establishes the connection between the "lower" and the "upper" domains of this universe. Rashi also explains the word קטורת as identical with the alternate name of Hagar, i.e. קטורה, to mean that her deeds were comparable to an incense offering because she "tied up" her door [euphemism for her vagina Ed.] and did not remarry until Sarah had died and Abraham was free to marry her (Genesis 25,1). Our sages suggest that Nadav and Avihu entered the Holy of Holies in order to teach a lesson concerning the mystical dimension of the incense-offering. They wanted to demonstrate that G–d anxiously awaits the prayers of the righteous. All of these notions are alluded to in Psalms 141,2: תכון תפלתי קטורת לפניך, "Take my prayer as an offering of incense before You." The subject of prayer teaches us the mystical dimension of the משפיע and the מושפע The latter prays with his eyes facing downwards while his heart is turned upwards toward G–d, the cause who turns His attention to what happens "down" here in our world. We in our hopes pour out our hearts heavenwards for He is the עילה, cause, whereas we are the עלולים, effects.

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.

We have a disagreement between Rabbi Chiyah and Rabbi Shimon in Yevamot 105b as to whether, while engaged in prayer, one has to look downwards with one's eyes or upwards. The former bases his opinion on the verse (Chronicles II 7,16) והיה עיני ולבבי שם כל הימים "My eyes and My heart shall always be there" [This is G–d speaking, concerning the Temple Solomon has built]. The latter bases his opinion on the verse in Lamentations 3,41, נשא לבבנו אל כפים אל א-ל בשמים, "We shall raise our hearts with our hands to G–d in heaven." While this discussion was in progress Rabbi Yishmael son of Rabbi Yossi joined the scholars, asking them what they were debating. When told that they discussed the manner in which to pray, Rabbi Yishmael quoted his father as having said that one needs to lower one's eyes when engaged in prayer, whereas one needs to focus one's heart heavenwards, in order to comply with both verses.