Does one commit a sin if he prays without the iqamah due to forgetfulness?

Q: If one forgets the iqamah and prays, does that affect this prayer? Whether he is praying alone or they are in congregation?
A: If the one praying alone or the congregation prays without the iqamah, the prayer is valid, and the one who did so must repent to Allah (Glorified and Exalted is He). Likewise, if they pray without the adhan, the prayer is valid; because the adhan and iqamah are collective obligations, and they are outside the core of the prayer.
And the one who left the adhan and iqamah must repent to Allah (Glorified and Exalted is He) for that; because regarding collective obligations, all are sinful for leaving them, and the obligation is lifted by some of them performing it. Among these are the adhan and iqamah: if enough people perform them, the obligation and sin are lifted from the rest; whether they are in residence or traveling, and whether they are in villages and cities or in the desert.
We ask Allah for all Muslims success in what pleases Him.