HerMES, the Herschel/SPIRE extragalactic GTO program, is detecting high redshift sources which were once the domain of high redshift QSOs. Our most spectacular object discovered to date, from over 50 square degrees of survey area with rich ancillary data, is an extraordinarily bright submillimeter galaxy with a confirmed redshift of z=6.337, which we call First Look Survey #3 (FLS3). This source is at a redshift close to the epoch of reionization, and it is most likely a signpost of the extreme evolution which fueled the transition from a neutral universe (the dark ages) to a completely ionized universe which we live in today. The epoch of reionization is the new frontier in structure formation, and the ability to select massive star formation-dominated galaxies in this era will lead to great advances in our understanding of the end of the dark ages. We have already measured the FIR luminosity, dust mass, dust temperature, rest-frame UV continuum, CO, H2O, and C+ line luminosities for FLS3. The last remaining physical characteristic to measure in order to understand the source is its stellar mass. Here we propose for two hour-long integrations of this source with IRAC CH1 and CH2 to robustly detect the source, measure its stellar mass, and constrain the UV extinction. These observations will enable us to determine stellar, dust, and gas mass ratios, and specific star formation rate. This single source will have major implications for our understanding of galaxy formation, the epoch of reionization, and the cosmic infrared background. These near infrared observations cannot be made with any other instrument. The high redshift value for this source was confirmed only after the last Spitzer call for proposals, and due to the overall uncertainty in the future Spitzer cycles and the paper reporting the discovery of this source now under preparation for publication in a high-profile journal, we request a rapid DDT observation.