Towards the end of the haftara for Parashat Vayeshev, the prophet Amos poses a number of rhetorical questions, beginning with, "Do two walk together if they had not first convened?" ("Ha-yeilkhu shenayim yachdav bilti im no'adu" – Amos 3:3). Ibn Ezra explains this verse as directed towards those who doubted the authenticity of the prophet's exhortations and warnings. When two people happen to arrive at a certain location at the precise same time, it can be guaranteed that they had previously agreed to convene at that place at that time. Similarly, if a prophet issues a warning and the forewarned events indeed transpire, then clearly he has been commissioned by God to deliver the message.
Rav Mendel Hirsch, in his commentary to the haftarot, suggests a different reading of this verse. He writes:
But, from that it follows that for Israel there should be no more serious pressing care than to carefully watch that it keeps the Torah of its God with unswerving loyalty. Nothing may be less left casually to chance. And that is just what here Israel is reproached with. If two people, and even if it were for the most unimportant purpose, wish to go on a journey to the same place together, do they leave meeting together and going off together just to chance? Do they not arrange and appoint a time, place and goal? And dare we leave our conduct with God casually to chance, just if by chance it happens to suit our convenience…
According to this approach, Amos' analogy refers to two people who embark on a certain journey or campaign together. Undoubtedly, if they want their journey or enterprise to succeed, they will carefully chart their course ahead of time and devise a detailed strategy. They will not leave any aspect of the mission to chance, and will instead invest time, thought and effort into planning every detail.
The prophet thus condemns the casual attitude exhibited by many towards Torah observance, the tendency to "play it by ear" and "see how things go" with regard to mitzvot. Amos, speaking in the name of God, noticed that the people left their avodat Hashem to chance, making it dependent upon circumstances rather than molding circumstances to the best of their ability to accommodate mitzva observance. Rav Hirsch notes in this context the warning repeated numerous times in the tokhechasection in Parashat Bechukotai (Vayikra 26:14-46) against "walking with Me be-keri," by chance. According to Rav Hirsch, this refers to a passive, casual attitude towards mitzvot, whereby one arranges his life as he wishes and thereafter decides whether and how Torah observance fits into the mix. Amos exhorts us to approach Torah observance with the same proactive, responsible attitude as people who "walk together" only after first devising a detailed strategy. Our observance of mitzvot cannot be dependent on our personal schedule; to the contrary, our personal schedule must be designed in such a manner that it allows us to fully meet all our religious responsibilities.