If the embodied one meets with death when Sattva is predominant, then he attains to the spotless worlds of the knowers of the Highest.
In simple words
Krishna explains what happens at death based on which force is strongest: "If purity is dominant when a person dies, they go to the pure, bright worlds of those who know the highest truth."
Word-by-word meanings
यदाwhenसत्त्वेin Sattvaप्रवृद्धेhaving become predominantतुverilyप्रलयम्deathयातिmeetsदेहभृत्the embodied oneतदाthenउत्तमविदाम्of the knowers of the Highestलोकान्to the worldsअमलान्of the spotlessप्रतिपद्यते(he) attains
14.14 यदा when? सत्त्वे in Sattva? प्रवृद्धे having become predominant? तु verily? प्रलयम् death? याति meets? देहभृत् the embodied one? तदा then? उत्तमविदाम् of the knowers of the Highest? लोकान् to the worlds? अमलान् of the spotless? प्रतिपद्यते (he) attains.Commentary Lokan Amalan Sptless worlds Brahmaloka and the like where Rajas and Tamas never predominate.The Highest Deities such as Hiranyagarbha.
Contemporary scholarly and practical interpretations for modern seekers.
This interpretation draws on a specific tradition and may not represent the view of any single school. For authoritative guidance within a specific tradition, seek a qualified teacher.
Modern
The existence and movement of the individual soul after death lie beyond the perception of the senses. Therefore, the truth of the principle expounded in this discourse cannot be verified through the senses while dwelling in this body. Yet when one undertakes a subtle examination of the mental conduct of human life in the present, there remains no doubt whatsoever regarding the rationality of this principle. A physician does not suddenly one day begin to contemplate some subtle problem of architecture, nor does an engineer overnight receive inspiration to treat cancer. At any given time, both individuals contemplate only those subjects consonant with their education and training.
Thus, even within the present body, we experience the continuity of intellectual life. This continuity is evident in the thoughts spanning years, months, weeks, days, and even each passing moment. Each moment's thought is merely an extension of the thought of the preceding moment. In this manner, if we clearly perceive in our intellectual life a distinct continuity and orderliness, whose integrity remains unbroken across past, present, and future, then at the time of death there is no logical reason for this chain to suddenly break. Death is merely a particular experience that may influence subsequent experiences. Yet this is nothing unprecedented, for every experience continuously influences the experience that follows it through its qualities and defects. Therefore, the movement of the soul after the abandonment of the body is determined solely by the combined result of all thoughts throughout life. Although its connection with this material world ceases, its intellectual life continues.
The Blessed Lord says: When the sattva guna becomes predominant and the soul departs from the body at that time, it attains the pure worlds of the most elevated beings. These are the worlds extending from heaven up to Brahmaloka. In Brahmaloka, because the influence of rajas and tamas is negligible, that world is supremely blissful.