The most important verse we recite in the Pesukei De'zimra section of our prayer service is, without doubt, the verse in Ashrei, "Potei'ach Et Yadecha U'masbi'a Le'chol Chai Ratzon." This verse literally means, "He opens His hand and graciously satiates all living creatures." It expresses our sense of dependence on God for our daily sustenance, and our belief that it is He who provides all living creatures, man and animal alike, with their basic needs.
The Sages comment that whoever recites this verse with concentration is guaranteed a share in the world to come, as he thereby affirms his trust and faith in God. For this reason, we add to Ashrei the verse, "Va'anachnu Nevarech Ka Mei'ata Ve'ad Olam Haleluy-a" ("And we shall bless God from now and forever…"). The actual paragraph of Ashrei concludes with the words "…Shem Kodsho L'olam Va'ed," but we add the verse "Va'anachnu Nevarech…" because it expresses our desire to praise God "from now and forever," even in the world to come. Since by reciting Ashrei, which contains the verse, "Potei'ach Et Yadecha," we guarantee our share in the world to come, it is appropriate in this context to express our wish to have the privilege of praising the Almighty even in the next the world.
On this basis, the Ben Ish Chai (Rabbi Yosef Chayim of Baghdad, 1833-1909) in Parashat Vayigash, Halacha 12, ruled that if one remembers at any point during Pesukei De'zimra that he had not concentrated during the recitation of this verse, he should repeat the verse at that point. Even if he has already reached "Va'yevarech David" or "Az Yashir," he should insert at that point the verse, "Potei'ach Et Yadecha…" with proper concentration. In fact, according to the Chesed La'alafim (work of Halacha by Rabbi Eliezer Papo, Bulgaria, 1785-1828), even if one remembered later in the service, for example after ‘Yishtabach’, he should say the Pasuk after the Amida, where he should begin from the pasuk right before "Potei'ach Et Yadecha…" starting at "Somech Hashem Likol HaNofleem."
The Sages ordained that we should recite Ashrei three times each day, twice during Shacharit and once during Mincha. The Abudarham (commentary on the Siddur by Rabbi David Abudarham, Spain, 13th century) explained, quite simply, that the Sages wanted to ensure that we would properly concentrate while reciting this verse at least once each day. By reciting it three times a day, we are almost assured to have the proper concentration at least on one occasion. The Rabbis did not require reciting Ashrei during the Arvit service because Arvit was initially established as an optional prayer. Therefore, had one of three daily Ashrei recitations been included in Arvit, those who chose not to recite Arvit would have lost one of the three recitations.
Summary: One must ensure to concentrate when reciting the verse, "Potei'ach Et Yadecha…" in the "Ashrei" paragraph during Pesukei De'zimra. If one remembers at some later point in the prayer service that he had not recited this verse with proper concentration, he should repeat the verse with concentration at the point when he remembers, even if this occurs after the Amida prayer.
