Krishna says, "When someone perceives the variety of living beings as rooted in One that has expanded Itself into the many, they then merge with 𝘽𝙧𝙖𝙝𝙢𝙖𝙣" (13.31). As per contemporary scientific understanding, the universe started about 14 billion years ago from a single point (singularity) and is expanding even today. This process of expansion created a large number of stars and planets. It also brought a variety of living beings into existence. This verse conveys the same using the language of its time.
While this knowledge can be easily attained, this verse indicates the ability to see 'One origin' in the present moment when we encounter different life forms and different situations created by them resulting in the triggering of many emotions within us. When we perceive 'One origin', we get freed from 'mine and yours' syndrome and in that sense, this verse also can be taken as a definition of 𝙈𝙤𝙠𝙨𝙝𝙖 which is the ultimate freedom here and now.
Krishna further says, "The 𝙋𝙖𝙧𝙖𝙢𝙖𝙩𝙢𝙖 (Supreme Soul) is imperishable, 𝙖𝙣𝙖𝙖𝙙𝙞 (without beginning), and 𝙣𝙞𝙧𝙜𝙪𝙣 (devoid of any 𝙜𝙪𝙣𝙖𝙨 -qualities). Although situated within the body, It neither acts nor is it tainted (13.32). The sky holds everything within it, but being subtle, does not get contaminated by what it holds. Similarly, 𝙖𝙩𝙢𝙖 (soul) which pervades the body is not affected by the attributes of the body" (13.33). To explain a similar intricacy, Krishna gave the example of the Lotus leaf which doesn't get wet despite being in contact with water. Similarly, the soul is also not affected by the attributes of the body.
The sky is all around us and it holds everything, but doesn't get contaminated because it neither gets attached to anything nor does it identify itself with something. It is about remembering this aspect whenever we see the sky and some meditation techniques use this aspect.